Architecture

"In the twentieth century, as in the twelfth, men's aspirations and longings may be correctly interpreted by the monuments they erect. For now as always the seen reveals the unseen; the material bodies forth the spiritual; thoughts are hidden until they find expression in tangible form. As the Gothic cathedral during the Dark Ages voiced the deep yearnings of devout souls, so the modern skyscraper as unmistakably reveals the secret springs of the world’s ceaseless activity, showing clearly what are the most important factors in the life of this age. The deity of to-day is the supposedly almighty dollar, and the towering structures of modern cities often serve as temples dedicated to mammon worship. They point a moral and teach a lesson as truly as the churches and castles that dotted mediaeval Europe."

"Thirty thousand feet above the earth / its a beautiful thing. everybody's a beautiful thing / mmm skyscraper, i love you."

"Crowned not only with no history, but with no credible possibility of time for history, and consecrated by no uses save the commercial at any cost, they are simply the most piercing notes in that concert of the expensively provisional into which your supreme sense of New York resolves itself"

"What is the chief characteristic of the tall office building? It is lofty. It must be tall. The force and power of altitude must be in it, the glory and pride of exaltation must be in it. It must be every inch a proud and soaring thing, rising in sheer exaltation that from bottom to top it is a unit without a single dissenting line."

"Architectural History is more than just the study of buildings. Architecture of the past and the present remains an essential emblem of a distinctive social system and set of cultural values, and as a result it has been the subject of study of a variety of disciplines."

"‘Architecture’ may at first appear to be a more fixed and finite term. It has a threedimensional, tangible, useable form. But questions remain about what can be considered architecture and what cannot, and by this I mean that we usually understand architecture to incorporate aesthetic as well as functional consideration into its structure. Anything that does not fall into this category can be described as ‘just a building’. This may seem too simple. Can architecture be determined solely by the use of refined architectural style – high or polite architecture instead of vernacular?"

"Architecture differs from a work of art, which can be displayed in different settings and the subject-matter, form and meaning will remain unchanged. The physicality of any built structure can be altered over time as additions and alterations are made. Moreover, a building or work of architecture can change its function as it meets the different demands of its occupants, although its exterior appearance may be unaltered. And its meaning may change depending on the nature of the context. This reveals some of the problems of interpreting historic architecture from a modern-day perspective as the physical changes and different cultural contexts transform the object."

"ARCHITECT, n. One who drafts a plan of your house, and plans a draft of your money."

"The civil engineer is the real 19th century architect."

"Windows and doors, in nameless sculpture drest, With order, symmetry, or taste unblest; Forms like some bedlam-statuary's dream, The craz'd creations of misguided whim."

"When, in architecture, one uses a fixed unit and combinations of it, to produce harmony, the effect should be most striking and apparent... as it is in music by the measured beat and in poetry by the cadence and rhythm."

"[Makes a good architect] an open mind, energy, an appetite for hard work, a willingness to explore new solutions and push boundaries. A sense of humor is also helpful."

"Bridges are America's cathedrals."

"Silently as a dream the fabric rose; No sound of hammer or of saw was there."

"Dancing and architecture are the two primary and essential arts. The art of dancing stands at the source of all the arts that express themselves first in the human person. The art of building, or architecture, is the beginning of all the arts that lie outside the person; and in the end they unite."

"Architects know that some kinds of design problems are more personal than others. One of the cleanest, most abstract design problems is designing bridges. There your job is largely a matter of spanning a given distance with the least material. The other end of the spectrum is designing chairs. Chair designers have to spend their time thinking about human butts."

"[A]rchitecture and psychology suddenly become very close."

"Architecture has recorded the great ideas of the human race. Not only every religious symbol, but every human thought has its page in that vast book."

"I felt a surge of annoyance. The palace was a monstrosity. It had towers, with pennants snapping in the breeze. It had triumphal staircases. It had flying buttresses. It had colonnades. What it didn't have was structure. It looked like an immense warehouse of architectural spare parts."

"Architecture worth great attention. As we double our numbers every 20 years we must double our houses. Besides we build of such perishable materials that one half of our houses must be rebuilt in every space of 20 years. So that in that term, houses are to be built for three fourths of our inhabitants. It is then among the most important arts: and it is desireable to introduce taste into an art which shews so much."

"A few centuries ago... the indigenous and often primitive architectural forms of that time had become suited to local climate through a long process of trial and error."

"Thirty spokes converge upon a single hub It is the hole in the centre that the purpose of the axle depends. We make a vessel from a lump of clay It is the empty space within the vessel that makes it useful. We make doors and windows for a room. But it is the those empty spaces that make the room habitable. Thus while the tangible has advantages It is the intangible that makes it useful."

"The architect Built his great heart into these sculptured stones, And with him toiled his children, and their lives Were builded, with his own, into the walls, As offerings unto God."

"We all see more of architecture than of any other art. Every street is a gallery of architects’ work, and in most streets, whatever their age, there is good work and bad. Through these amusing shows many of us walk unperceivingly, all our days, like illiterates in a library, so richly does the fashionable education provide us with blind sides ."

"Anon, out of the earth a fabric huge Rose, like an exhalation."

"Nor did there want Cornice or frieze with bossy sculpture graven."

"The hasty multitude Admiring enter'd, and the work some praise, And some the architect: his hand was known In heaven by many a tower'd structure high, Where scepter'd angels held their residence, And sat as princes."

"Follow the architectural history of any city, and you will find it during the last half-century the sorrowful record of a pitiful destruction. The great gardens are always the first thing sacrificed. They are swept away, and their places covered by brick and mortar with an incredible indifference. Fine houses, even when of recent construction, like the Pompeiian house of Prince Napoleon in Paris, are pulled down out of a mere speculative mania to build something else, or to cut a long, straight street as uninteresting and as unsuggestive as the boxwood protractor which lies on a surveyor's desk."

"Architects and engineers are among the most fortunate of men since they build their own monuments with public consent, public approval and often public money."

"Thus when we view some well-proportion'd dome, * * * * * * No single parts unequally surprise, All comes united to th' admiring eyes."

"The modern age has in most cases failed with the rebuilding of old cities destroyed in the war and shown itself incapable of recreating the complex grain of places which took centuries to evolve. Clearly our modern architectural vocabulary just isn't up to the job."

"When we mean to build, We first survey the plot, then draw the model; And when we see the figure of the house, Then must we rate the cost of the erection."

"'Fore God, you have here a goodly dwelling and a rich."

"He that has a house to put's head in has a good head-piece."

"La vue d'un tel monument est comme une musique continuelle et fixée qui vous attend pour vous faire du bien quand vous vous en approchez."

"An architect, to be a true exponent of his time, must possess first, last and always the sympathy, the intuition of a poet … this is the one real, vital principle that survives through all places and all times."

"No complete architecture has yet appeared in the history of the world because men, in this form of art alone, have obstinately sought to express themselves solely in terms either of the head or of the heart. I hold that architectural art, thus far, has failed to reach its highest development, its fullest capability of imagination, of thought and expression, because it has not yet found a way to become truly plastic: it does not yet respond to the poet's touch. That it is today the only art for which the multitudinous rhythms of outward nature, the manifold fluctuations of man's inner being have no significance, no place."

"The true architectural art, that art toward which I would lead you, rests, not upon scholarship but upon human powers; and, therefore, it is to be tested, not by the fruits of scholarship, but by the touch-stone of humanity."

"I call architecture frozen music."

"Architecture has its political Use; publick Buildings being the Ornament of a Country; it establishes a Nation, draws People and Commerce; makes the People love their native Country, which Passion is the Original of all great Actions in a Common-wealth…. Architecture aims at Eternity."

"And so, as they kept coming together in greater numbers into one place, finding themselves naturally gifted beyond the other animals in not being obliged to walk with faces to the ground, but upright and gazing upon the splendor of the starry firmament, and also in being able to do with ease whatever they chose with their hands and fingers, they began... to construct shelters."

"Houses are built to live in, not to look on; therefore, let use be preferred before uniformity, except where both may be had."

"There was King Bradmond's palace, Was never none richer, the story says: For all the windows and the walls Were painted with gold, both towers and halls; Pillars and doors all were of brass; Windows of latten were set with glass; It was so rich in many wise, That it was like a paradise."

"Old houses mended, Cost little less than new, before they're ended."

"A man who could build a church, as one may say, by squinting at a sheet of paper."

"The Gothic cathedral is a blossoming in stone subdued by the insatiable demand of harmony in man. The mountain of granite blooms into an eternal flower, with the lightness and delicate finish, as well as the ærial proportions and perspective of vegetable beauty."

"Earth proudly wears the Parthenon As the best gem upon her zone."

"The hand that rounded Peter's dome And groined the aisles of Christian Rome, Wrought in a sad sincerity: Himself from God he could not free; He builded better than he knew; The conscious stone to beauty grew."

"Middle wall of partition."

"An arch never sleeps."

"Die Baukunst ist eine erstarrte Musik."

"Rich windows that exclude the light, And passages that lead to nothing."

"No hammers fell, no ponderous axes rung, Like some tall palm the mystic fabric sprung. Majestic silence."

"When I lately stood with a friend before [the cathedral of] Amiens,… he asked me how it happens that we can no longer build such piles? I replied: "Dear Alphonse, men in those days had convictions (Ueberzeugungen), we moderns have opinions (Meinungen) and it requires something more than an opinion to build a Gothic cathedral."

"So that there was neither hammer nor axe nor any tool of iron heard in the house, while it was in building."

"Grandeur * * * consists in form, and not in size: and to the eye of the philosopher, the curve drawn on a paper two inches long, is just as magnificent, just as symbolic of divine mysteries and melodies, as when embodied in the span of some cathedral roof."

"In the elder days of Art, Builders wrought with greatest care Each minute and unseen part; For the gods see everywhere."

"Ah, to build, to build! That is the noblest of all the arts."

"The stone which the builders refused is become the head stone of the corner."

"It was stated, * * * that the value of architecture depended on two distinct characters:—the one, the impression it receives from human power; the other, the image it bears of the natural creation."

"I would have, then, our ordinary dwelling-houses built to last, and built to be lovely; as rich and full of pleasantness as may be within and without: * * * with such differences as might suit and express each man's character and occupation, and partly his history."

"Therefore when we build, let us think that we build (public edifices) forever. Let it not be for present delight, nor for present use alone, let it be such work as our descendants will thank us for, and let us think, as we lay stone on stone, that a time is to come when those stones will be held sacred because our hands have touched them, and that men will say as they look upon the labor and wrought substance of them, "See! this our fathers did for us.""

"Architecture is the work of nations."

"No person who is not a great sculptor or painter, can be an architect. If he is not a sculptor or painter, he can only be a builder."

"Ornamentation is the principal part of architecture, considered as a subject of fine art."

"Since it [architecture] is music in space, as it were a frozen music…. If architecture in general is frozen music."

"Behold, ye builders, demigods who made England's Walhalla [Westminster Abbey]."

"He who builds in the streets must allow himself to get dirty."

"Improvement makes strait roads: but the crooked roads without Improvement are roads of Genius."

"A physician, a civil engineer, and a computer scientist were arguing about what was the oldest profession in the world. The physician remarked, "Well, in the Bible, it says that God created Eve from a rib taken out of Adam. This clearly required surgery, and so I can rightly claim that mine is the oldest profession in the world." The civil engineer interrupted, and said, "But even earlier in the book of Genesis, it states that God created the order of the heavens and the earth from out of the chaos. This was the first and certainly the most spectacular application of civil engineering. Therefore, fair doctor, you are wrong: mine is the oldest profession in the world." The computer scientist leaned back in her chair, smiled, and then said confidently, "Ah, but who do you think created the chaos?""

"Men build bridges and throw railroads across deserts, and yet they contend successfully that the job of sewing on a button is beyond them. Accordingly, they don’t have to sew buttons."

"The civil engineer is the real 19th century architect."

"Mechanical differs from Civil Engineering in the fact that the former provides or makes what the latter uses. On this account, a knowledge of mechanical engineering is of invaluable service to the civil engineer, and it should be the rule to obtain this practically, whatever branch of engineering the student may ultimately follow."

"His father loved him dearly, but his work, that of a civil engineer, had left him with but little time for his family. Energetic, active, and always taken up with some responsible work, he did not spoil his children with excessive tenderness."

"The form a city assumes as it evolves over time owes more to large-scale works of civil engineering - what we now call infrastructure - than almost any other factor save topography."

"No greater care is required upon any works than upon such as are to withstand the action of water; for this reason, all parts of the work need to be done exactly according to the rules of the art which all workmen know, but few observe."

"Go for civil engineering, because civil engineering is the branch of engineering which teaches you the most about managing people. Managing people is a skill which is very, very useful and applies almost regardless of what you do."

"Mechanical engineering is now the largest branch, with nearly 40 percent of the profession's members. Civil engineering, which was the largest branch prior to World War II, has dropped to second place, with about 25 percent of all engineers."

"Bhakra Nangal Project is something tremendous, something stupendous, something which shakes you up when you see it. Bhakra, the new temple of resurgent India, is the symbol of India’s progress."

"If you can’t reduce a difficult engineering problem to just one 8-1/2 x 11-inch sheet of paper, you will probably never understand it."

"A great bridge is a great monument which should serve to make known the splendour and genius of a nation; one should not occupy oneself with efforts to perfect it architecturally, for taste is always susceptible to change, but to conserve always in its form and decoration the character of solidity which is proper."

"From the laying out of a line of a tunnel to its final completion, the work may be either a series of experiments made at the expense of the proprietors of the project, or a series of judicious applications of the results of previous experience."

"Comparatively few engineers are good mathematicians; and... it is fortunate that such is the case; for nature rarely combines high mathematical talent, with that practical tact, and observation of outward things, so essential to a successful engineer. There have been... brilliant exceptions; but they are very rare. But few even of those who have been tolerable mathematicians when young, can, as they advance in years, and become engaged in business, spare the time necessary for retaining such accomplishments. Nearly all the scientific principles which constitute the foundation of civil engineering are susceptible of complete and satisfactory explanation to any person who really possesses only so much elementary knowledge of arithmetic and natural philosophy as is supposed to be taught to boys of twelve or fourteen in our public schools."

"Mechanical Engineering is applicable rather to works connected with private enterprise, such as the designing and construction of steam machinery for the purposes of navigation and transportation, the adaptation of such machinery to mills and factories, the construction of water-wheels, the fabrication of materials, iron, steel, and brass, for the purposes of the engineer, the architect, and manufacturer ; and the manufacture of implements and machinery for agriculture, for mining, and for domestic purposes. But the prominent feature of Mechanical Engineering, that which contributes more than any other to elevate it to the rank of a liberal or learned profession, and at the same time separates it from the science of Civil Engineering, is, that all its operations relate to power, motion, and work."

"There is nothing in machinery, there is nothing in embankments and railways and iron bridges and engineering devices to oblige them to be ugly. Ugliness is the measure of imperfection."

"This morning I came, I saw and I was conquered, as everyone would be who sees for the first time this great feat of mankind."

"Ten years ago the place where we are gathered was an unpeopled, forbidding desert. In the bottom of a gloomy canyon, whose precipitous walls rose to a height of more than a thousand feet, flowed a turbulent, dangerous river. The mountains on either side of the canyon were difficult of access with neither road nor trail, and their rocks were protected by neither trees nor grass from the blazing heat of the sun. The site of Boulder City was a cactus-covered waste. The transformation wrought here in these years is a twentieth-century marvel."

"We are here to celebrate the completion of the greatest dam in the world, rising 726 feet above the bed-rock of the river and altering the geography of a whole region; we are here to see the creation of the largest artificial lake in the world—115 miles long, holding enough water, for example, to cover the State of Connecticut to a depth of ten feet; and we are here to see nearing completion a power house which will contain the largest generators and turbines yet installed in this country, machinery that can continuously supply nearly two million horsepower of electric energy."

"I know it works for me. As we cross the bridge — the burning bridge — With flames behind us, We front the line. It's you and me, baby, against the world."

"By the rude bridge that arched the flood, Their flag to April’s breeze unfurled, Here once the embattled farmers stood, And fired the shot heard round the world. The foe long since in silence slept; Alike the conqueror silent sleeps; And Time the ruined bridge has swept Down the dark stream which seaward creeps."

"When you're weary Feeling small When tears are in your eyes I will dry them all I'm on your side When times get rough And friends just can't be found Like a bridge over troubled water I will lay me down."

"The Berlin Wall was not dismantled by rulers and agreements but rather by citizens who felled it with their own hands."

"The world is full of the markers of abandoned empires, from Hadrian’s Wall to the Great Wall of China, from the remnants of the one in Arizona to the remnants of the one in Berlin."

"And I have known the eyes already, known them all— The eyes that fix you in a formulated phrase, And when I am formulated, sprawling on a pin, When I am pinned and wriggling on the wall, Then how should I begin To spit our the butt-ends of my days and ways? And how should I presume?"

"I think it more likely I am spending an unnecessary amount of money in the foundation walls, but I content myself with the reflection that a hundred years hence it will be all the same to me, and the building the better because of my extravagance."

"A person who thinks only about building walls, wherever they may be, and not of building bridges, is not Christian."

"Before I built a wall I’d ask to know What I was walling in or walling out, And to whom I was like to give offence. Something there is that doesn’t love a wall, That wants it down."

"There are frequent moments when we feel lower than the lowest of mankind, and this opinion of ourselves isolates us. Hence the rumor that all flesh is base comes almost as a message of hope. It breaks down the wall that has kept us apart, and we feel one with humanity."

"All in all it's just another brick in the wall. All in all you're just another brick in the wall."

"But it was only fantasy. The wall was too high, As you can see. No matter how he tried, He could not break free. And the worms ate into his brain."

"Beyond walls are lakes and plains, canyons and the universe"

"There is a very small remnant ... of worthy disciples of philosophy. ... Those who belong to this small class have tasted how sweet and blessed a possession philosophy is, and have also seen and been satisfied of the madness of the multitude, and known that there is no one who ever acts honestly in the administration of States, nor any helper who will save any one who maintains the cause of the just. Such a savior would be like a man who has fallen among wild beasts—unable to join in the wickedness of his fellows, neither would he be able alone to resist all their fierce natures, and therefore he would be of no use to the State or to his friends, and would have to throw away his life before he had done any good to himself or others. And he reflects upon all this, and holds his peace, and does his own business. He is like one who retires under the shelter of a wall in the storm of dust and sleet which the driving wind hurries along; and when he sees the rest of mankind full of wickedness, he is content if only he can live his own life and be pure from evil or unrighteousness, and depart in peace and good will, with bright hopes."

"THE CIVILIZATION OF ancient Greece was nurtured within city walls. In fact, all the modern civilizations have their cradles of brick and mortar. These walls leave their mark deep in the minds of men. They set up a principle of 'divide and rule' in our mental outlook, which begets in us a habit of securing all our conquests by fortifying them and separating them from one another. We divide nation and nation, knowledge and knowledge, man and nature. It breeds in us a strong suspicion of whatever is beyond the barriers we have built, and everything has to fight hard for its entrance into our recognition."

"A prison wall was round us both, Two outcast men we were: The world had thrust us from its heart, And God from out His care: And the iron gin that waits for Sin Had caught us in its snare."

"Gaudí was drawn not just to the aesthetics of the catenary but also to what it represented mathematically. His use of catenaries made the structural mechanics of a building a principal feature of its design. Gaudí realized that the entire architecture of a building could be drafted using a model of hanging chains... when he was commissioned to design a church the Colònia Güell... he made an upside-down skeleton of the project. Instead of using metal chains, he used string weighed down by hundreds of sachets containing lead shot. The weight of each sachet on the string created a mesh of 'transformed' catenary curves. The arches of these transformed catenaries were the most stable curves to withstand a corresponding weight at the same position (such as the roof, or building materials)."

"In 1690... Jacob Bernoulli brought up the problem of the catenary in a memoir... in the '...Huygens' solution represents the past... a complex, though skillful, geometrical method. Leibniz, using his new [infinitesimal calculus] reaches a correct analytical formula...y/a = (b^\frac{x}{a} + b^\frac{-x}{a})/2 where a is [a] segment... and b... corresponds to... e... ...supplied two correct constructions ...presents valid statistical arguments and... new and important... equations of equilibrium in differential form. ...In 1697-1698, Jacob Bernoulli was the first to derive the general equations that not only solved the problem, but also permitted the treatment of the more general theme of the equilibrium of a flexible rope, subject to any distribution of tangential (f_t) and normal (f_n) forces. Bernoulli's equations are...\frac{dT}{ds} + f_t = 0, \qquad \frac{T}{r} + f_n= 0where T is the tension, s the curvilinear abscissa, and r the radius of curvature."

"The largest catenary structure of masonry is the Great Hall of the Palace of Taq Kisra, at Qesiphon, then the capital of Persia."

"The trolley-wire must... be suspended with only a very small sag, and to obtain this result without excessive tension in the wire the span must be relatively short, i.e. of the order of 10 ft. to 15 ft. It is obvious that for these short spans the method of construction adopted in tramway practice would be unsuitable, both from the mechanical as well as the electrical standpoint. However, by adopting the catenary system—that is, supporting the trolley-wire from another wire, suspended with considerable sag between supports of moderate span—we are able to obtain a level trolley-wire with a relatively small number of supporting structures. The wire from which the trolley-wire is supported is called the "catenary" or "messenger" wire, and by insulating this wire from the supporting structures there is no necessity for insulated hangers on the trolley-wire."

"Within a shed erected on the construction site of the church of the Sagrada family... Gaudí... made an upside-down model using lightweight cables to represent the structural lines of the future church—a model based on the structural notion of the inverted catenary. ...Analogically represented by little pouches filled with lead pellets the action of the stresses has been done ...The resulting chain configurations are used to determine the geometrical shapes and structural profiles of columns, pillars, arches, and vaults. ...Vicens Vilarrubias i Valls took photos of the model ...Gaudí used these photos upside-down to draw over them the external and internal elevations, studies of details and sections of the building."

"Corol. 6.—In a vertical plane, but in an inverted situation, the chain will preserve its figure without falling, and therefore will constitute a very thin arch or fornix: that is, infinitely small, rigid, polished spheres, disposed in an inverted curve of a catenaria, will form an arch no part of which will be thrust outwards or inwards by other parts, but, the lowest parts remaining firm, it will support itself by means of its figure... none but the catenaria is the figure of the true and legitimate arch or fornix. And when the arches of other figures is supported, it is because in their thickness some catenaria is included. ...From Corol. 5... it may be collected, by what force an arch or buttress presses a wall outwardly, to which it is applied. For this is the same with that part of the force sustaining the chain, which draws according to a horizontal direction. For the force which in the chain draws inwards, in an arch equal to the chain drives outwards. All other circumstances, concerning the strength of walls to which arches are applied, may be geometrically determined from this theory, which are the chief things in the construction of edifices."

"What has been objected by an anonymous author, in the Leipsic Acts of Feb. 1699, in his animadversions on my demonstrations concerning the catenary, is this: that I have undertaken to demonstrate, after my manner, a matter found out and published by others seven years ago. This is true, and I cannot find any thing in it that is blame worthy. Those great men Huygens, Leibnitz, and Bernouilli, have discovered and communicated many properties of the catenaria, but without demonstration. I have contrived demonstrations, which was the thing I undertook to do. But was this matter that is the nature and primary properties of the catenaria all found out and published by others? ...From all ages architects have made use of arches in public buildings, as well for strength as beauty. Yet what was the true geometrical figure of an arch was not known before my demonstrations came out."

"It was comparatively late that the theory of arches attracted the notice of mathematicians. Dr. Hooke gave the hint, that the figure of a perfectly flexible cord or chain, suspended from two points, was the proper form for an arch. Galileo considered the catenary as a parabolic curve, and John Bernouilli appears to have been the first who discovered its nature. Dr. Gregory (Phil. Trans. 1697) published an investigation of its properties, and observes that the inverted catenary is the best form for an arch on account of its lightness. This is true so long as it is not pressed by an extraneous weight. It is not, however, capable of bearing a load on any part, much less of being filled up on the spandrels, which must be the case in practice. Other considerations must be involved before it can be fitted to receive a roadway or other weight, either upon its crown or haunches."

"The flexible chain, hanging under the action of applied force, will assume a certain shape, namely the catenary if the chain is subjected only to its own weight, or a if the load is uniformly distributed horizontally. Whatever the load, there will be a corresponding shape, and the structural action in all cases is the same; purely tensile forces are transmitted along the centre line of the chain."

"As Hooke saw in 1675 with his ut pendet continuum flexile, sic stabit contiguum rigidum inversum, ...a hanging chain may be inverted to give a satisfactory arch to carry the same loads, but working in compression rather than tension. The compressive arch, however, if of vanishingly small thickness, would be in unstable equilibrium, and stability is conferred in practice by making the arch ring of finite depth. Now if purely compressive forces, without bending, are to be transmitted from one portion of the arch to the next (as purely tensile forces are transmitted in the chain), then the arch centre line can accept only a single type of loading. Thus a parabolic arch can carry only a uniformly distributed horizontal load (although the magnitude of the load is arbitrary). It is the depth in a real arch which enables the arch to carry wider ranges of loading; a large number of different idealized centre-line arches can be contained within a given practical profile. ...[T]his must be so, or no mediaeval bridge would have survived its decentering."

"The true Mathematical and Mechanical Form of all manner of Arches for building with the true butment necessary to each of them, a Problem which no Architectonick Writer hath ever yet attempted, much less perform'd. ...Ut pendet continaum flexile, sic stabit contiguum rigidum, which is the Linea Catenaria."

"I will begin with the subject of your bridge... and it is with great pleasure that I learn... that the execution of the arch of experiment exceeds your expectations. ...You hesitate between the catenary and portion of a circle. I have lately received from Italy a treatise on the equilibrium of arches, by the Abbé Mascheroni. It appears to be a very scientifical work. I have not yet had time to engage in it; but I find that the conclusions of his demonstrations are, that every part of the catenary is in perfect equilibrium. ...I would propose that you make your middle rail an exact catenary, and the interior and exterior rails parallels to that. It is true, they will not be exact catenaries, but they will depart very little from it; much less than portions of circles will."

"The Catenary has its name from Catena, a chain; being the curve which a regular and very flexible chain will assume, if suspended loosely from both ends. It seems to have been first noticed by the famous Galileo, who proposed it as the figure of an arch of equilibration, but unfortunately mistook it for a . In fact, the Catenary, near its vertex, differs insensibly from that curve, but afterwards deviates more considerably. ...the Parabola diverges faster from its axis than the Catenary. The error of Galileo in confounding those two curves was not perceived till , in 1669, ascertained, by actual experiment, that the Catenary is neither a Parabola nor an . It was in 1691, that the penetrating genius of James Bernoulli discovered the true nature of the catenarian curve. A similar investigation was soon produced by John Bernoulli, by Huygens, and by Leibnitz. This latter philosopher, whose powers of invention and stores of learning were alike transcendant, discovered the fine relation of the Catenary to the Logarithmic Curve."

"The most difficult properties of the Catenary were revealed before the close of the seventeenth century. This curve is entitled to particular attention, not only because it throws light on the theory of arches, but because it applies directly to the construction of suspended bridges, which are now deservedly coming into repute."

"A non-catenary curve might be perfectly doable, but it takes more material, it has bigger beam sections, and overall it is much more complicated to construct... Even if the cladding falls out, the interiors and everything else falls away and the whole thing turns to dust and rubble and sand, [the catenary] should still stand."

"I love the catenary because it tells the story of holding up the roof."

"The arch is one of those brilliant innovations... Spanning... with horizontal beams is a losing game. ...By converting all the stress that fractures the middle of... stone beams—technically tension—into compression on stone piers larger... spaces could be spanned. ...But shift the pressure even slightly off center, and the pillar is likely to collapse. ...In their early incarnations, the limitations of both arch and dome was the ability of craftsmen to shape the stones carefully enough to create blocks precisely in the wedge shapes needed for a particular arch. Despite their mathematical sophistication in most other respects, the architects of antiquity lacked a proper geometric solution to the ideal form of the arch. (It was not until 1675 that the English polymath Robert Hooke described mathematically the shape of an arch loaded in pure compression, that is, with no tension, by showing how it describes an upside-down version of the catenary curve of a hanging chain.) As a result, the only way they could design an arch, and its component stones, was completely by eye, and... such tolerances commanded high prices. Rome overcame this drawback with typical ingenuity, first replacing stones and mortar... and expensive stonecutters with relatively cheap bricklayers. Even more ingeniously, some anonymous Roman builder found how to combine the mortar—in Latin pulvis puteoli—with lime, sand, and gravel to make the first concrete. ...The concrete domes of Rome were not surpassed until the age of steel."

"Certainly the most striking contemporary example of a similar form [ arch] is to be found in St. Louis' ... In its incredible scale and construction out of metal plates this structure also serves as a convenient reminder of the important developments of the production of iron and steel that took place during the Industrial Revolution and that have so significantly affected arches as well as all other types of structural forms for the past 150 years."

"Concrete being such a fluid and dynamic material... finds its identity once it is contained. ...A few... who used the forming materials at hand [were]... Antoni Gaudi... ... ... Felix Candela... ... ... Miguel Fisac... Many of these early innovators pushed the computational envelope... Some, like Antoni Gaudi, looked to nature for inspiration. The question... Do we need to "reinvent forming" or just draw from nature, i.e., gravity—catenary action? as Gaudi did. Alan Chandler in fabric framework notes "...for Felix Candela and Christopher Alexander fabric acted as a permanent shutter (framework)..." Chandler speaks of the family of fabric construction that includes... s... Pneumatic structures... Hydrostatic structures and... Shell structures derived from membrane form-finding. When faced with extremely complicated and complex shapes Heinz Isler and Antoni Gaudi used fabric as a modeling tool. These visionaries recognized that hanging chains and fabrics, forming catenaries, are in pure tension and when inverted are in pure compression and very stable. Gaudi, whose ing preceded the works of Candela... looked to nature and natural forms—an approach today called biomimicry..."

"One can roll noncircular wheels over appropriate road surfaces. The most striking example of this is the fact that a can roll on a road that consists of linked catenaries (the catenaries are defined by y = - cosh x) ...(the ride is not smooth in the sense that the center does not move forward at a constant rate of rotation, but... the actual ride... feels quite smooth). This animation was inspired by an exhibit at San Francisco's ..."

"Thin shells — Three-dimensional spatial structures made up of one or more curved slabs or folded plates whose thicknesses are small compared to their other dimensions. Thin shells are characterized by their three-dimensional load-carrying behavior, which is determined by the geometry of their forms, by the manner in which they are supported, and by the nature of the applied load."

"[T]he early work of Lambot... was one of the first applications of , but [was] also... a form of . His patent on wire-reinforced boats that was issued in 1847... This was the birth of reinforced concrete, but subsequent development differed from Lambot’s concept. The technology of the period could not accommodate the time and effort needed to make mesh of thousands of wires. Instead, large rods were used to make what is now called conventional reinforced concrete, and the concept of ferrocement was almost forgotten for 100 years."

"In the twentieth century, lightly reinforced brick shells were inspired by timbrel vaulting, a common building method in the Mediterranean. ... upon emigrating to the United States from in 1881, introduced the method with great success. His son, Rafael Guastavino, Jr. ...appears to be the first to have introduced steel reinforcing to thin brick shells. ...[T]wo patents... [1910, 1913] documented this system, which is a precursor to the thin shells of reinforced concrete developed widely in the ensuing decades."

"has designed some of the most striking thin shells in reinforced concrete of the second half of the twentieth century. He creates thin shells by hanging small membranes in tension and creating smooth curving surfaces that are then inverted and scaled up to create large-scale structures in compression. ...Within the constraint of economy, he discovered new forms from purely structural considerations and demonstrated the unlimited possibilities for thin compression shells to be found in hanging models."

"Candela did not invent the concrete shell; nor is he the first to make use of the hyperbolic paraboloid... Other people... have contributed more to the theoretical analysis of shell structures. But nobody else can claim credit for such an exciting variety of shell structures... [H]e has concentrated his effort in one particular sphere: the construction of light concrete roofs."

"Candela] is not just an engineer, or an architect, or a contractor and constructor, but all three... [W]hen he thinks out a new scheme, the method of construction and its economy is constantly in his mind. ...He prefers to obtain his economy by using his inventive skills as an engineer to reduce... material... [H]e recognizes the value of ... but he is also very conscious of its limitations. Especially is he skeptical about the value of the theory of elasticity as applied to concrete... of... calculations suggesting an accuracy which is purely fictitious... Designing... proceeds from a structural feeling acquired by experience and guided by rough calculations, a refinement of design... further analysis... and so on. ...[A] flair for making the right guess yields quicker and better results than a lot of mathematics... this is no reason for despising theoretical analysis... But one cannot design by theory..."

"[M]ost of Candela's structures are almost complete in themselves... the forms and proportions bear witness to his artistic sensibility. ...[B]alanced perfection ...makes a... structure into a work of art. ...[T]he whole must take precedence over any of its parts."

"The method of geometric modeling of multi-shell roofs depends mostly on the surface's properties forming the shell; their curvature, as well as continuity between them. ...s play a specific role, due to their characteristics. Catalan surfaces are s... They are oblique ruled surfaces which can be divided into two groups... second order—hyperbolic paraboloid... [and] of more than second order—s, cylindroids... The difference between hyperbolic paraboloid, conoid, and cylindroid results from different path of movement of a surface's ruling during formation. In all cases of Catalan surfaces' creation... each ruling is parallel to the fixed plane (not containing the surface's directrices)."

"... all through school had a reputation of working alone and of doing his work in an unusual way. ...in 1950 he graduated with a degree in civil engineering. For his final-year design project, he chose to study thin shells... Following graduation... he helped [Pierre] Lardy with teaching, and also worked on the many cases of structural failure [both at his alma mater, the Federal Technical Institute]... When Isler left his position... he considered... [a] career as a painter, but challenged by shell design problems... while doing free-lance engineering work.. in late 1954, he designed a pneumatic form, thin shell factory for the Trösch Company. It was the first work in which he set the form completely on his own. In 1955, at an international congress in Amsterdam, he presented publicly for the first time his new designs..."

"Torroja was a specialist in stress analysis... and he wrote a... book on the mathematical theory of elasticity. This... led him to see a connection at Algeciras between the stresses in the shell and the reinforcement... but not to express those stresses in... visually evident ribs. We contrast... Nervi's Little Sports Palace... whereas Nervi sees shells as ribbed, Torroja sees them as ribless... since domes tend to spread, Nervi designed ribbed buttresses... whereas Torroja avoids buttresses by connecting vertical supporting columns with a... polygonal ring of horizontal ties... prestressed to counteract dead load and to lift the shell slightly off its scaffold... probably the first application of prestressing to a doubly curved shell. In the Nervi dome... the buttresses are supported below ground on a ring which carries the horizontal thrust and... transmits the vertical weight to the ground. ...[These] choices related to the [respective] local traditions in Italy and Spain."

"The idea of form over mass also developed in Europe in the pioneering work of Dyckerhoff and Widmann... in Weisbaden, Germany. Working in reinforced concrete, the firm experimented with new ways to cover large spaces in the 1920s. The firm built domes and cylindrical "barrel" shells to serve as large roofs of extraordinary thinness. The possibilities... fascinated an Austrian civil engineering student, Anton Tedesko... who joined the firm in 1930."

"The Hershey Arena... Tedesko designed a thin reinforced concrete, barrel-shell roof, three and one-half inches thick, supported across its width by eight arches. ...A roof posed a different problem than a bridge or dam. On a bridge, live load from traffic is significant, and a dam must resist the live load of water on its upstream face. On a long-span concrete roof, live load (mainly rain and snow) is a small fraction of the dead load of the structure itself. Tedesko realized that the supporting arches did not need to be of uniform depth. ...[he] designed the arches to be able to... support the entire roof load, including the thin shell and all of the live load. He also made calculations to show that the thin shell could carry its own weight and the live load without help from the arches, except near their lowest edges. It was thus a conservative design..."

"Shells were not being done in the United States at all, and I started seeing pictures of these buildings coming out of South America... Italy and Spain... they happened to be all Latin countries. ...I thought, "God, how do I do this?" you know, these three-dimensional curved structures... [T]he greatest of them all... was Nervi... I found out that I couldn't find out how to design... them. ...I realized after many years of striving that a lot of them really didn't know how to design them. They were just doing it intuitively, and that was not satisfactory to an engineer. I needed to know a rational way of doing it, and that sent me back to school and... to studying... [I]t took me years and years of very hard intellectual work to find ways to do this. ...[W]hen I finally did it, I was one of the few guys in the country that had really made that much effort, and so I became a pioneer..."

"In 1958, Felix Candela completed his most significant work, the Los Manantiales Restaurant shell, in Xochimilco, Mexico City. ...[He] was taking a risk... The form was original, unexplored, and impossible to analyze precisely. Candela’s career, however, habitually flew in the face of precise analysis. In his first acclaimed shell, the Cosmic Ray Pavilion of the University of Mexico City, he also designed an unprecedented form, using almost no calculation... Candela’s subsequent designs relied increasingly on structural understanding and practical experience. As a designer-contractor, he had the unique responsibility of building his own solutions. By closely observing his buildings, and using smaller projects to test new ideas, he developed an acute sense of concrete shell behavior."

"The essential ingredients of a shell structure... are continuity and curvature. ...[S]hells are structurally continuous in the sense that they can transmit forces in a number of different directions in the surface of the shell... These have a quite different mode of action from skeletal structures... only capable of transmitting forces along discrete structural members. ...There seems to be a principle that closed surfaces are rigid. This principle is used in many areas of engineering construction. ...[A]lthough the ideas of 'closed' and 'open' shells... are fairly clear, it is difficult to quanitify intermediate cases into which... the majority of actual shell structures fall. ...There is a theorem, due to Cauchy, which states that a convex polyhedron is rigid. ...[N]on-convexity may produce deformability. ...While rigidity and strength are in many cases desirable attributes of shell structures, there are some important difficulties which can occur... [involving] unavoidable rigidity. ...[A] second broad principle... may be stated thus: efficient structures may fail catastrophically. Here I use the term 'efficient' to describe the consequences of employing the first principle. By designing a structure as... closed... we may be able to use thinner sheet material, and hence produce an economical, or efficient, design."

"For around 2000 years single and double curved shells structures, such as barrel and vault s, have been used to cover large spans in buildings. Until the twentieth century these were generally constructed either from masonry or some form of unreinforced concrete, materials strong in compression but relatively weak in tension. Well known examples such as the Pantheon... ... Santa Maria del Fiore... and St. Peter's Basilica... have a span to thickness ratio of less than 50 to 1, which is relatively thicker than a... typical hen's egg. ...[T]he stone vaulting of... medieval Gothic cathedrals... demonstrate the mason's art in the construction of... complex masonry shells. With the advent of reinforced concrete... strong in both compression and tension, it became possible... to construct thin shells with much higher span to thickness ratios... commonly... in the region of 500 to 1."

"At the time of construction of the Wyss shell, three-dimensional computer software was not available and it would have been extremely difficult to convey, using only normal engineering drawings, the required form of the concrete at the feet of the shell... To overcome the problems... proposed that, rather than making sketches, drawings, or even a model of the detail, they should resort to modelling it at full-scale on site."

"At the beginning, the was not covered by any type of roof. During the reconstruction... in 1964... the roof covering... was created. ...reinforced by cotton threads and covered by rubber layers. The material underwent large rheological displacements. In... 1968... catastrophe occurred, caused by wind and high humidity. In the eighties... a polyester fabric, intended only [for] seasonal application, was used. ...age and... repeated disassembling of the membrane caused its gradual destruction. ...In 2007 ...complete rebuilding ...assumed the roof to be a permanent structure. ...[V]erification of ...internal forces was conducted in 2012 ...by team."

"The resistant virtues of the structure that we make depend on their form; it is through their form that they are stable and not because of an awkward accumulation of materials. There is nothing more noble and elegant from an intellectual viewpoint than this; resistance through form."

"The emergence of lightweight structures can be traced back to the second half of the nineteenth Century. This period witnessed the advent of new material technologies such as steel, , resistant glass and, later, fabric membrane. Together with advances in analysis and design tools, engineers and architects have been challenged to build increasingly lighter structures. ...[A] pioneering structure was the lattice tower by... in 1896. In the 1920s, Anton Tedesko first introduced reinforced concrete thin shells in the United States. This expansion was pursued... by , and André Paduart... The limit of lightness was achieved with tensile structures constructed of prestressed cable nets and fabric membranes; the strength coming from the anticlastic curvature of the geometric surface. ...Nowadays, lightweight structures should be designed... by including the multitude of design contraints. This will result in hybrid systems lying at the boundary of different typologies."

"Nature does not apply the construction principle of a beam supported by two s. Forms developed by nature are following the rational attempt to achieve distinct functionalities with the smallest possible material - and energy consumption. An impressive example is the phenomena of egg shells... The shell principle is adopted by humans... in building construction, in order to achieve wide spanning and material saving 'slender' structures."

"The design of shells... implicates the design of internal stress fields of form dependent shapes... meeting the compatabilites of all boundary conditions..."

"The title of first pioneer of the HP hyperbolic paraboloid or hypar construction] in concrete in the 1930s belongs to Fernand Aimond for the projects that he constructed.., for the formulation of the theoretical structural membrane model, and for his influence both on [Giorgio] Baroni in Italy in the late 1930s and on Candela in Mexico in the 1950s."

"[[w:Membrane theory of shells|[M]embrane theory]]... is the theory of shells whose bending rigidity may be neglected. The spectacular simplification... makes it possible to examine a wide variety of shapes and support conditions. In particular, the stress problems of tanks and shell roofs... There is, of course a heavy penalty... [T]he inadequacies... can be discovered by a critical inspection of the... solutions, without any need for... solving the bending problem—a task which is often out of the reach of the practical engineer and even of the research worker. On the other hand, membrane theory is more than a first approximation... If a shell is so shaped and so supported that it can carry its load with a membrane stress system, it will be thin, light, and stiff and, therefore, the most desirable solution to a design problem. Membrane theory will guide the shell designer toward such structure."

"Shell-like structures are familiar enough in nature but the use of such structures as containers, aircraft fuselages, submarine hulls and roofing structures is only of recent origin. That the inherent strength of shells... has not been utilised much in the past is probably due to the difficulty in obtaining suitable material... [S]hell structures in general are these days constructed of such varied materials as steel, light alloy, plastics, wood and reinforced concrete. ...[T]o simplify analysis it will be assumed that the material... is homogeneous, isotropic and perfectly elastic. ...[A]lthough reinforced concrete behaves in a reasonably elastic manner only in the lower stress ranges the majority of reinforced concrete shell roofs that are constructed in practice are designed as elastic structures."

"The true Mathematical and Mechanical Form of all manner of es for building with the true butment necessary to each of them, a Problem which no Architectonick Writer hath ever yet attempted, much less perform'd. ...Ut pendet continaum flexile, sic stabit contiguum rigidum, which is the Linea Catenaria."

"The meandor compression spring... or corrugated spring... is a promising design variant for compression axle springs of composite material... The middle surface of the meander spring is the... "." ...[T]he middle surface ...is the ...[i.e.,] can be unrolled onto a flat plane without stretching or tearing it. ...[A] developable surface ...in three-dimensional space and ...complete ...is necessarily ruled. This property is of primary importance for manufacturability... The meander spring... is modeled for mechanical analysis as a thin shell."

"My invention shows a new product which helps to replace timber where it is endangered by wetness, as in wood flooring, water containers, plant pots, etc. The new substance consists of a metal net of wire or sticks which are connected or formed like a flexible woven mat. I give this net a form which looks in the best possible way, similar to the articles I want to create. Then I put in hydraulic cement or similar bitumen tar or mix, to fill up the joints."

"Cement Hall, Swiss National Exhibition, Zurich (1939)... was built by architect and engineer Hans Leuzinger and ... to demonstrate the potential of thin shells. ...The width of this parabolic shell is 50.32 ft... built by the Gunite method, [it] is only 2.36 in thick. ...A sculptural piece by Robert Maillart entititled "Endless Ribbon" [1935-1936]... is a thin shell built of reinforced concrete. This... can be classified within Constructivism or... constructive spatial art. [I]t represents... the direct correlation between the language of sculpture and that of modern thin-shell architecture that moves the sensitive engineer such as Maillart to express himself also as a sculptor. Maillart's structural shells as a whole testify to this similarity of language... He was the father of flared columns connecting with floor slabs to eliminate supporting beams and designed unique bridge forms. Maillart's name remains associated with innovative concrete forms that extend to the structural virtuosity of thin shells."

"Like Candela, Isler has concentrated his practice on thin s... Isler derives his forms not from analytical geometry (as were Candela's hypars) but directly from physical and funicular models - flexible membranes that assume the least energy, or minimal surface, for a specific boundary and force patterns. In the mid-1950s Isler invented two new form-making techniques, the first by using pneumatic models and the second by experimenting with hanging cloth models sprayed with water and put out to freeze in wintertime. Later, in 1965, he added a third technique that made shapes "by the flow method, by... the advancing velocity of a liquid inside a tube... At the wall, velocity is zero because of friction, whereas in the center there is maximum velocity... and forms a dome shape." While the frozen cloths conform to the funicular shape given by gravity, the other methods, pneumatic and flow, are hydraulic."

"There is... [a] need to code cheaper and accessible programs in line with using sustainable methods to better the livelihood of mankind. To address this issue a theory is formulated based on the Euler-Bernoulli beam model. This model is applicable to thin elements which include plate and membrane elements. This paper illustrates a finite element theory to calculate the master stiffness of a curved plate. The master takes into account the stiffness, the geometry and the loading of the element. The of this is established from which the load which is unknown in the matrix is evaluated by the principle of bifurcation."

"It was the great nineteenth century mathematician, Carl Gauss who proved mathematically that any curved surface, natural or man-made, can be characterized as only one of three different possible shapes: as -like, -like, or saddle-like. All three of these geometric shaped can be used as the basis for thin-shell structures."

"[T]he basic assumption in the linear theory of shells that the displacements of the shell are considered to be small in comparison to the thickness is abandoned in the present nonlinear analysis of shells. A shell is called thin if the maximum value of the ratio h/R, where h is the thickness of the shell and R is the principal radius of curvature of the middle surface... is less than or equal to 1/20 ...beyond this range... the shell is regarded as thick. ...in a large number of practical applications the ratio... lies in the range between 1/50 and 1/1000, making the theory of thin shells of great practical importance. In this chapter the nonlinear equations... in terms of orthoganal are derived assuming the material... is isotropic, homogeneous, and elastic. An important simplification based on the assumption that second invariant of the median surface strains in the expression for the extensional ... can be neglected, originally made by [Noah] Burger, is introduced to derive a simplified set of nonlinear... differential equations."

"Concrete being such a fluid and dynamic material... finds its identity once it is contained. ...A few... who used the forming materials at hand [were]... Antoni Gaudi... ... ... Felix Candela... ... ... Miguel Fisac... Many of these early innovators pushed the computational envelope... Some, like Antoni Gaudi, looked to nature for inspiration. The question... Do we need to "reinvent forming" or just draw from nature, i.e., gravity—catenary action? as Gaudi did. Alan Chandler in fabric framework notes "...for Felix Candela and Christopher Alexander fabric acted as a permanent shutter (framework)..." Chandler speaks of the family of fabric construction that includes... s... Pneumatic structures... Hydrostatic structures and... Shell structures derived from membrane form-finding. When faced with extremely complicated and complex shapes Heinz Isler and Antoni Gaudi used fabric as a modeling tool. These visionaries recognized that hanging chains and fabrics, forming catenaries, are in pure tension and when inverted are in pure compression and very stable. Gaudi, whose ing preceded the works of Candela... looked to nature and natural forms—an approach today called biomimicry..."

"Shells under compressive loading investigated under the assumption of perfect properties may be considered to be optimal structures. Their load carrying capacity is significantly larger compared to shells which show deviations in geometry, material behaviour, loading and boundary conditions. ...Unfortunately, comparatively little quantitative information exists about the initial imperfections in actual structures... One possibility to improve this situation is to perform systematic numerical simulations... Classical numerical concepts of the load carrying capacity of imperfect structures focus on the model of a perfect shell configuration and on the analytical estimation of unstable, postcritical equilibrium paths. This was first demonstrated by Koiter, whose postbuckling theory describes the nonlinear static load carrying behaviour of structures in the initial stages of buckling. ...[I]nitial unfavourable imperfections will lead to a reduction in load carrying capacity. This approach has certain restrictions as the results are evaluated by linearisation around the bifurcation point of the perfect shell. For the numerical simulation of the load carrying behaviour of imperfect shells it is commonly assumed that the initial geometric imperfections have the shape of the lowest bifurcation mode of the respective shell. ...In the cases of high imperfection sensitive shells [with] multi-mode-buckling... the lowest bifurcation mode is not always the ”worst” imperfection shape. Recently, a specific concept employing finite element procedures... directly evaluates the ”worst” imperfection shape and [is based upon] analysis of the imperfect shell space."

"Resistance of Spherical Shells to an Internal Fluid Pressure.—An elastic fluid contained in a closed vessel presses each unit of area of the surrounding walls with equal force. The resistance offered by the walls depends on their superficial area, their form, their thickness, and the coefficient of resistance of the material."

"The hollow sphere encloses the largest space in proportion to the superficial area of its shell, and all vessels that are not spherical, exposed to an internal fluid pressure, experience distortion on account of their tendency to assume the spherical form. A hollow sphere, having a shell of uniform thickness composed of a homogeneous material, experiences the same tension at all sections of metal formed by diametrical planes."

"The area of a [circular] diametrical section, S, of a thin spherical shell is very nearly given by formula:S = 2 \pi rtwhen t represents the thickness, and r = the inner radius of the shell, and t is supposed to be very small compared with r. The whole force, F, to be resisted by the tenacity of section S is equal to the excess of the internal fluid pressure per unit of area over the external pressure, into the area of the plane passing through this section, orF = \pi r^2 pAssuming that every portion of section S is equally strained by F, and designating by k the coefficient of the ultimate tenacity of the material of which the shell is composed, the bursting pressure will be found from the equation: \pi r^2 p = 2 \pi rtk; hencep = \frac{2tk}{r} { I.}and the proper ratio of the thickness to the radius of a thin hollow sphere is given by the formula:\frac{t}{r} = \frac{p}{2k}..."

"Resistance of Cylindrical Shells to an Internal Fluid Pressure.—The tension produced in a cylindrical shell by an internal fluid pressure may be considered as being of two different kinds—viz., first, a tension acting in a longitudinal direction, tending to pull the ends of the cylinder apart; and, secondly, a tension acting in a diametrical direction, tending to split the cylinder from end to end."

"The force, F, producing the first-named tension is represented by the formula:F = \pi r^2 p;and the sectional area, S, of a thin shell resisting this force may be represented with sufficient accuracy, as in the case of thin spherical shells, by the formula:S = 2 \pi rt.The value of p, when it becomes the bursting pressure, is found from the equation,r^2 \pi p = 2 \pi rtk; hence p = \frac{2tk}{r} { II.}the same as that of a spherical shell of equal radius and thickness."

"To find the value of p which would split the cylinder [of unity length] from end to end... The force tending to rupture such a ring at the sections formed by any diametrical plane is given by formula:F = 2rp,and the area of these sections byS = 2t.The bursting pressure is, therefore, found from the equation:2rp = 2tk; hence p = \frac{tk}{R}...only half as great as... equation { II.}"

"Resistance of Cylindrical Shells to an External Fluid Pressure.—Thin hollow cylinders exposed to an external fluid pressure never give way by direct crushing, but by collapsing; it may be assumed that, other things equal, the resistance of tubes to collapsing is greater as their form is more truly cylindrical and their shell more perfectly homogeneous."

"Fairbairn has deduced the following formula from experiments made mostly on very thin cylindrical tubes of various lengths and diameters—viz., for wrought-iron cylindrical tubes let l = the length, d = the diameter, and t the thickness of the shell, all expressed in the same unit of measure, and let p = the collapsing pressure in pounds per unit of area; thenp = 9,672,000 \frac{t^{2.19}}{l d}. { IV.}In case a tube is stiffened by T-iron rings or by flanges, l represents the distance between two such adjacent rings or flanges."

"Fairbairn finds that the collapsing pressure of... an elliptic form of cross-section is found approximately by substituting... for d the [following]... let a be the greater and b the less semi-axis of the ellipse; then we are to maked = \frac{2 a^2}{b}. { V.}"

"In an article in the Annales d'u Génie civil, March, 1879, on the “Resistance of Tubes subjected to an External Pressure,” by Théodore Belpaire, an attempt has been made to deduce a new formula for the collapsing strength of tubes. ...The writer ... considers the case of a tube with ends rigidly fixed, and supposes that under an external pressure it changes its form in such a manner that its generatrix becomes the arc of a circle, the centre of which lies on a perpendicular erected in the centre of the generatrix; and, neglecting, the elastic forces due to flexure or elongation of the fibres—which are very small as long as the curvature is slight—he investigates the shearing stresses; these attain their greatest value at the fixed ends. Calling S the greatest shearing stress, p the pressure in pounds per square inch, t the thickness of the tube in inches, L the length of the tube in inches, he deduces the following approximate formula for the external pressure which a given tube can bear with a degree of safety depending on the value attributed to S—viz.:p = \frac{2tS}{L}. { VI.}The writer deduces then a general value S from two experiments made by Fairbairn with elliptical tubes, because the uncertain and variable elements of strength due to the cylindrical form and to homogeneity of the material do not enter here. When the factor of safety in the foregoing equation is to be four, the value of S becomesS = 428,394 \frac{t}{D} - 7,111,550 (\frac{t}{D})^2;...With reference to those cases where the factor of safety exceeded four greatly, the writer claims that the high pressures necessary to produce collapse indicate merely the great increase of strength derived in the particular instances from the uncertain element of circular form."

"The problem of curved plates or shells was first attacked from the point of view of the general equations of Elasticity by H. Aron. He expressed the geometry of the middle-surface by means of two parameters after the manner of Gauss, and he adapted to the problem the method which Clebsch had used for plates. He arrived at an expression for the potential energy of the strained shell which is of the same form as that obtained by Kirchhoff for plates, but the quantities that define the curvature of the middle-surface were replaced by the differences of their values in the strained and unstrained states."

"E. Mathieu adapted to the problem [of curved plates or shells ] the method which Poisson had used for plates. He observed that the modes of vibration possible to a shell do not fall into classes characterized respectively by normal and tangential displacements, and he adopted equations of motion that could be deduced from Aron's formula for the by retaining the terms that depend on the stretching of the middle-surface only."

"Lord Rayleigh... concluded from physical reasoning that the middle-surface of a vibrating shell remains unstretched, and determined the character of the displacement of a point of the middle-surface in accordance with this condition. The direct application of the Kirchhoff-Gehring method led to a formula for the potential energy of the same form as Aron's and to equations of motion and boundary conditions which were difficult to reconcile with Lord Rayleigh's theory. Later investigations have shown that the extensional strain which was thus proved to be a necessary concomitant of the vibrations may be practically confined to a narrow region near the edge of the shell, but that, in this region, it may be so adjusted as to secure the satisfaction of the boundary conditions while the greater part of the shell vibrates according to Lord Rayleigh's type."

"[P]rinciples as developed by Kelvin and by Love show that it is impossible to bend a nearly flat dish shaped shell about one horizontal axis without at the same time bending it in the opposite direction about a second horizontal axis at right angles to the first."

"[P]icture... a circular piece of a plate which has an approximately spherical curvature at its center point O. Pass a plane XY tangent to the surface at O and let OZ be normal to it at O. Then if a be applied about OX it will not only make the curvature of the plate greater in the plane ZOY but at the same time it will make its curvature less in the plane ZOX to an equal amount as is evident by experiment on a shell of any elastic material, and as is proven in Gauss' theorem of the curvature of thin shells. Since the force applied to produce the given bending moment must produce both these equal changes of curvature simultaneously by producing elongations and compressions in twice as much material as in a plane plate of equal cross section, each of them is only half as great as would be produced in a plane plate in a single direction by this same moment. Hence it. appears that the deformations produced by an applied moment are not more than half as great in a spherical dish shaped plate as in a plane plate..."

"The at any point P of a curved surface is most readily measured by finding the radii of curvature of two curved plane sections of the surface made by a pair of planes drawn normal to the surface at P and at right angles to each other. Normal planes are those perpendicular to the surface at P, and they intersect each other in the normal to the surface at P. If R is the radius of curvature of any plane section at the point P, then 1/R is defined as its curvature at P. At every point of a convex surface there must, except in case when the curvature of all of the sections is the same, be some one of the normal sections in which the curvature is the greatest, and also another section in which the curvature is least. These are called principal planes and s. According to Euler's Theorem these principal sections lie in normal planes which are at right angles to each other, and further, the sum of the curvatures of any pair of rectangular normal sections whatever, at a given point P is constant, so that in rotating a pair of normal planes that remain perpendicular to each other about the normal the increment of the curvature of either normal section is equal to the decrement of the other, and the sum of the two normal curvatures is equal to that of the principal curvatures."

"In his great treatise on the Mathematical Theory of Elasticity Love, following the original investigations of Gauss, demonstrates... that when a piece of a thin elastic shell or plate that has a spherical curvature of 1/R is deformed by a small bending without stretching, then in the case of initial spherical curvature one principal curvature of the deformed surface will exceed the initial curvature 1/R by the same amount as the other will be less than l/R. That this is the fact in this case seems evident without following the abstruse analysis of Love... because if x and y be lines drawn tangent to two rectangular normal sections at P, and the spherical surface be bent slightly about x so as to alter the curvature of the section in the normal plane at right angles to x by alternately increasing and decreasing it, it is evident from symmetry that the curvatures of the section in the normal plane at right angles to y will undergo at the same time alterations of curvature which are equal and opposite to those in the first normal plane, altho this equality does not in general hold true in shells that are not spherical in shape. Nevertheless, the same statement evidently holds true for surfaces of revolution about the normal at P as an axis."

"[C]onsider the bending moments that must be applied to produce such a deformation. It is evident from the fundamental equation EI/R = M of the ordinary theory of thatEI\;d(\frac{1}{R}) = dMis the equation which expresses the relation between the increment (or decrement) of curvature d(1/R) and the increment (or decrement) dM of the applied moment which produces this change of curvature about x (or y) in which the value of I may be calculated in case of only slight curvature just as in a flat plate."

"It is evident that in order to produce this kind of deformation it is sufficient to apply one positive and one negative moment increment, each of the same magnitude dM, simultaneously about each of the rectangular axes x and y, respectively. These moments produce elongations and shortenings in the exterior and interior fibers of the plate or shell independently in two directions at right angles to each other in the same manner as in a beam but none whatever are produced in the neutral surface, so that the resistance that is offered to this bending arises from the resistance which the fibers offer to such elongation and shortening. The principal curvatures of the surface after bending will be 1/R + d(1/R) and 1/R - d(1/R) respectively."

"[S]uppose a uniform thin-walled hemisphere... is subjected only to its own weight, and is supported round its [base] by forces which produce compressive stresses σ. If the shell has radius a and thickness t, and the material has unit weight ρ, then [the force applied to the base is equal to the weight of the structure, where 2\pi a is the circumference and 2\pi a^2 is the surface area of the hemisphere]\sigma(2\pi at) = \rho(2\pi a^2t) or [dividing by 2\pi at] \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \sigma = \rho aThus the compressive stress necessary to support the dome has a magnitude independent of the thickness of the dome. ...Now the expression \rho a ...is typical of the order of magnitude of stresses in more general shapes of shell... [I]t may be expected that externally applied loads will at most equal, and will usually be less than the self-weight loads of shells of reasonable size. ...Thus stresses resulting from snow or wind may be expected to be of the same order as those resulting from dead load."

"Very thin shells may be in danger of locally. The problem hardly arises for civil engineering applications over moderate spans, but may be very important if the spans are very large. Local buckling of a thin shell will occur at a typical stress\sigma_{cr} = kE \frac{t}{R}where E is [and R is the minimum radius of curvature of the shell]. The value of the constant k varies from author to author, but a reasonable value is about 0.25. Thus for a concrete shell for which E is about 20 000 N/mm2, and for which \frac{t}{R} is as small as 1/1000, the critical stress is determined as say 5 N/mm2."

"[S]ome will claim that they give the best service to engineers by concentrating mainly on the form and structure of the governing equations... for once the foundations have been laid properly (they say), the solution of all problems becomes merely a mathematical or computational exercise... and indeed unless the foundations have been laid properly (they say), any resulting solutions are of questionable validity. Another group will argue... they can serve engineers best by providing a set or 'suite' of computer programmes, which are designed to solve a range of relevant problems... and... such programmes renders obsolete... the theory of shell structures... I have rejected both... the important thing is for engineers to understand how shell structures behave..."

"Any load which is applied to the shell is sustained in general partly by the stretching surface and partly be the surface; and the balance in load-sharing is regulated mainly by the 'interface pressure' between the two surfaces, which varies from point to point over the surface. This interface pressure becomes a prime variable of the problem. In terms of classical it is a variable 'redundancy'."

"Gauss (1828) pointed out that there are two distinct but complimentary ways of thinking about the of surfaces. ...this point ...is absolutely fundamental to a clear understanding of the subject. Gauss's dual view of curvature fits precisely the 'two surface' description, and it provides succinctly the geometrical conditions which are necessary if the deformation of the two surfaces is to match. The key variable in this connection turns out to be a scalar quantity; and paradoxically... conventional treatment... in terms of general is... too elaborate to reveal this crucial... quantity."

"The development of the plastic theory of structures from the 1930s onwards was healthy not only because many real materials are still structurally useful when they have passed beyond the elastic range, but also because the new theory was able to shift the emphasis... to more profound questions about the kind of information which the engineer requires in order to design satisfactory structures. ...plastic theory can contribute to the understanding of the response of shells to localized loading."

"The essential ingredients of a shell structure are continuity and '. ...an ancient masonry or vault is not obviously continuous... it may be composed of separate... sub-units or s not necessarily cemented... But in general... are held in a state of compression throughout... thus in compressive contact... [S]hells are structurally continuous in the sense that they can transmit forces in a number of different directions in the surface of the shell, as required. These structures have a quite different mode of action from skeletal structures... [which are] only capable of transmitting forces along their discrete structural members."

"[T]he basic model of a shell which we shall use... takes as its first step the replacement of a shell by a surface... [M]uch of the detail of the stress distribution will be suppressed precisely in the step of shrinking the three-dimensional physical shell into a zero-thickness surface. ...[T]he 'surface' theory... is extremely simple in comparison with other theories... [T]he regions in which the theory is inadequate are all highly localized, and there are very many practical problems in which... the local details are either unimportant or else can be treated more or less in isolation. All if this is closely analogous to the classical methods for analyzing beam and frame structures."

"The analysis and design of shell structures is of interest in... the design of large-span roofs, liquid storage facilities, silos... pressure vessels, including nuclear reactor containment vessels and pipes... structural design of aircrafts, rockets and aerospace vehicles. All... require the analysis and design of shells... [T]he derivation of equations for plates or shells is only an extension of... bars or beams, based on equilibrium, , and . ...Using the understanding of shell behavior... including the approximate methods and... tables for quick solutions... a reader may be able to judge the computer results, before designing a shell structure. ...Theory of circular rings, concepts of stress resultants and middle surface are... introduced... Circular also forms an intermediate step for a gradual introduction or transition to shell analysis from the analysis of bars and beams."

"[A] shell element will have, in general, 10 unknown internal stress reactants... [B]y making suitable assumptions, we try to obtain simpler a solution... for practical purposes. We first assume that the shell is thin. Such shells are... very flexible for resisting bending moments and shearing forces. ...We would always prefer the shell to resist any loading by development of in-plane forces... we assume that the moments Mx, My, Mx,y and My,x are zero... Then, by taking moments about the x- and y-axes... we conclude that Qy and Qx must also be zero, and by taking moments about the z-axis, we get Nxy = Nyx. Thus there remain only three unknown internal stress resultants, Nx, Ny, and Nxy, to support a given loading. Also... three equations of equilibrium\sum_{} F_x = 0 \quad \sum_{} F_y = 0 \quad \sum_{} F_z = 0...determine the three unknowns. Such simplified theory... is called membrane theory, as opposed to the more general and complex bending theory..."

"[W]e can consider the general equation for the deflection [w] of a shell as\mathcal{L}[w(x,y)] = f[p(x,y)]where \mathcal{L} is a and f[p] is some function of the given loading p. The general solution... will bew = w_h + w_pwhere w_p is the particular solution... that satisfies equilibrium and compatibility at all internal points... but not necessarily satisfying the boundary conditions. ...w_h is the solution of the homogeneous equation with p = 0 (...only edge loads can be present). ...[F]or solving practical problems, we can [find] w_p...by assuming moments and shears to be zero... the "membrane solution." ...similar to obtaining (fairly correctly) the forces in Truss members by assuming moments and shears in the members as zero (i.e., assuming the joints are perfect pins)... For obtaining w_h... we must... use the exact differential equation... the "bending theory" solutions... Fortunately, for most types of shells, they die out quickly as we move away from the boundaries. ...[O]ur general procedure ...obtain membrane forces under a given loading... then superimpose... the bending theory solutions for edge loads. ...[T]he membrane and edge-load solutions together satisfy the boundary conditions; i.e., the edge loads are obtained by solving equations of compatibility at the boundaries."

"A revival of interest in curvilinear structures is under way... es, vaults, and thin-shelled structures must be re-discovered. ...Why is there a revival in shell structures, and where might it lead? Cost factors, materials availability, labor supply, housing crises, solutions to domestic and Third World problems all play a part... With today's almost unlimited computer technology and the knowledge that can be gained from understanding s and vaults built both in the past and present, it is hoped that this work on the practical aspects of designing curvilinear forms will contribute to further exploration and encourage the application of thin shells..."

"A thin shell is a special kind of vault whose geometry may include many shapes. ...a three-dimensional form made thicker than a membrane, so that it can not only resist tension as membranes do, but also compression. On the other hand, a thin shell is made thinner than a slab, which makes it unable to resist bending, as a slab does. In short, thin shells are structures thicker than membranes, but thinner than slabs. Thin shells are made possible by the use of materials that work well under tension and compression. Masonry has no tensile strength... Only the availability of and made a thin shell possible."

"The of a shell can be of the same sign throughout... In such a case the surface is called synclastic. s are synclastic surfaces... The curvature of a shell can also be of a different sign... both concave and convex... which is known as anticlastic. An example... is the hyperbolic paraboloid."

"While size and support conditions have an important bearing on the degree of accuracy needed in the analysis, the distribution of load has a less important effect on stresses. This is due to the fact that s in the shell are more closely related to the boundary conditions than to the load. Hence, it is usually unnecessary to analyze a thin shell for partial live loads even though the supporting members must be analyzed for such partial loads. For this reason, snow load on thin shells may be assumed either uniformly distributed on the horizontal projection or uniformly distributed over the surface of the shell. On the other hand, local bending moments due to large concentrated loads on the shell must be considered."

"Shells of double curvature both the synclastic... and anticlastic... are inherently better suited to resist loads by direct forces than are shells of single curvature. The reason for this is obvious from the fact that this type of shell possesses arch action along both curvatures. But in order that surfaces curved in two directions behave as a shell, it is important that proper support or edge members be provided. The direct stresses throughout the major portion of the shell are usually of little significance except as they relate to . A careful evaluation should be made of the bending moments produced in the vicinity of the edge members by the interaction of the edge member and the shell. For moderate size shells, this effect usually is confined within a few feet of the vicinity of the edge member. ... An exception to this are some anticlastic shells, like the hyperbolic paraboloid, wherein bending can prevail throughout a greater portion of the shell. To a limited extent, this also occurs in s, when the supports do not provide a reaction tangent to the shell surface. In these cases, the bending moments may extend a significant distance into the shell."

"The great era of thin concrete shells... was an attempt to cover large spans with the most widely used construction material of the Twentieth Century and yielded structures that are now regarded as architectural masterpieces. The design of thin concrete shells also fostered theoretical developments in , in the mathematical theory of shells and in the theory of finite elements."

"In Belgium, the key figure in the design, construction and popularisation of concrete thin shells was certainly André Paduart (1914-1985). ...Paduart was also and particularly an active member of the International Association for Shells Structures (IASS) founded by E. Torroja in Madrid in 1959. ...[He] organized in Brussels in 1961 one of the very first symposia of this association... Shortly after, he published [1961] in French a remarkable small book covering essential theory, design and construction of thin concrete shells [Introduction au calcul et a l' exécution des voiles minces en béton armé]... translated in English [Introduction Shell Roof Analysis] in 1966..."

"[A] significant breakthrough was achieved with... two celebrated huge airship hangars built by Freyssinet at Orly in the early 1920s... [whereby] the principle of the corrugated form for the concrete shell was introduced to obtain the necessary stiffness..."

"Cylindrical s have probably been the most used form of concrete shells. The reconstruction after the devastations of the Second World War required forms of building which offered economy of material. This gave an enormous boost to the use of shell roofing... since materials... were in short supply... [N]early 50000 square meters of warehouses at the docks of harbour [were built] between 1947 and 1950...by [André] Paduart and [C.] Wets... [H]angars were built 1950-1952 at... airfields... one arch of a hangar under construction at Chièvres collapsed... a [short] time after decentering. ...[M]easurements made in the early 1990s [indicated that] several of the [arches] at Chièvres ...were significantly deformed."

"For the 1958 Brussels international exhibition, Paduart and architect J. Van Dooselaere received an official commission... to design a structural symbol testifying of the "victory of [Belgian] civil engineering over nature"... The final structure... the "Civil Engineering Arrow" [Pavilian of Civil Engineering], was a spectacular thin wall... cantilever beam... a bold impression of equilibrium and "tour de force". [They] received the 1962 Construction Practice Award for their "Arrow". ...dismantled in 1970."

"Paduart was working at the edge between academia and engineering practice. ...[H]is production during thirty years... is eclectic, with s, corrugated shells, hypar shells and folded plates. He could teach... mathematical theory of shells at the university, but used... very simple methods derived from the Strength of Materials to design his own shells. This did not deter him from conceiving bold structures, at the limits of the utilization of the materials and construction techniques of his time, but he looked always forward with anxiety to the decentering of the shells..."

"Shells can be singly curved (e.g., cylinders and cones) or doubly curved (e.g., sphere or hyperbolic paraboloid)."

"[A] hyperboloid of one sheet... is often used for s, because it can be formed of straight lines... Another doubly curved shape formed of straight lines is the ... for which a straight line travels along another straight line at one end and a curve at the other end."

"At any point on a surface, there are two principal radii of curvature that uniquely define the surface. Of all the curves on the surface that can be drawn through the point, the two principal radii of curvature will be the maximum and minimum that can exist at the point. The maximum radius of curvature for a is infinity, while [its] minimum is the radius of the circle..."

"[Take] two pieces from the outside and inside of a , respectively. In the former, both radii of curvature lie on the same side of the surface, and [so] the curvature is considered positive, while in the latter they are on opposite sides of the surface, and [therefore] the curvature is negative."

"All shells have either positive (bowl-shape) or negative (saddle-shape) curvature. ...Positive curvature shells are subject to , as the entire shell is subject to compression forces. In contrast, material failure is more common in negative curvature shells with brittle materials such as concrete."

"The structural analysis of shells has had a long and difficult history."

"Shells were developed and reached their peak popularity just before the ready availability of computers and the FE method."

"The analysis of shells requires that the three conditions of equilibrium, compatibility, and constitutive laws be satisfied simultaneously. The latter are the stress-strain properties for the materials.... Most shells are designed with isotropic materials."

"With the development of advanced composites, their orthotropic and anisotropic behavior must be considered. However, composites have not been used for architectural shells to date."

"Roof structures are seldom designed for dynamic loads. Earthquake and wind loads may be treated as equivalent static loads."

"The above three conditions result in three partial differential equations, two of the 2nd order and one of the 4th order, for the most general case with two different radii of curvature and with combined bending and membrane actions. An early representation of these equations for cylindrical shells may be found in Donnell (1933). Bradshaw... extended those equations to the general case of double curvature, which can describe any 1D member (beam), 2D member (plate), or 3D singly or doubly curved member (shell)."

"If the 4th order -related terms are left out, the equations will represent only the membrane action, which is usually sufficient for part of the shell away from the s because flexural resistance of thin shells contributes little in this region."

"Equal radii of curvature result in equations for a . Equations of a cylindrical shell are derived when one radius of curvature is set to infinity; when both are set to infinity, it will result in bending of a flat plate. Finally, the ordinary differential equation for bending of a beam is derived when plate width is set to unity."

"Stress analysis of complete shells, such as s, is much simpler than for architectural roofs because of the boundary conditions."

"When the shell is a portion of the sphere, it tends to spread outward at the discontinuous edge. To counteract this a ring is added, but the ring and the shell distort by different amounts, which results in stresses in the shell. These incompatible strains must be reconciled analytically, which is not too difficult a task for simple spherical shells. However, when the shell has isolated supports and few (if any) planes of symmetry, it is a severe problem..."

"The resulting disturbance at the edge may be thought of as causing stress redistributions to flow across the entire shell with diminished effect as they move away from the edge."

"In many cases... the stresses resulting from the discontinuous edges will dominate the design."

"Ribs are frequently added at the edges, though visually disruptive. One of the graceful aspects of Candela’s shells is their lack of ribs. It is also possible to design the shell with the rib integrated within the shell itself."

"There is a remarkable property of shells supported vertically at their edges. [Take] a spherical dome supported on a wall. A tension tie is required around the perimeter at the intersection of the dome and the wall. This tie will be funicular, i.e., it will only carry axial tension forces. This principle has been known since antiquity for circular domes and ties. However... the tie will be funicular for any shape of either the plan or elevation (Csonka 1962) provided that the shell has positive curvature and continuous vertical support. The support may be a continuous wall or stiff beams between adequately spaced columns. ...The thrusts are taken by shear forces through the width of the shell, and only tension forces exist in the tie."

"Beles and Soare... have reported [on] buckling failure of shells. Unlike shells of positive curvature that are subject to buckling, in shells of negative curvature, such as hyperbolic paraboloids, buckling is prevented through the tension curvature in the other direction."

"Virtually all studies on shell buckling have focused on cylindrical, conical, and spherical shells made of metals, and usually on full 360° models rather than the much more complex architectural shells. ...Applicability of these tests to large-scale concrete shells... is questionable."

"Initial imperfections in shells can result in their at loads far below their theoretical capacity. Once a shell buckles, its collapse tends to be complete, contrary to plates, which have high post-buckling capacity."

"When is placed on a , the weight distorts the balloon. This means the shell will not be exactly the initial shape of the balloon. This is not important for a small span shell. For a long span shell, however, this deviation from the spherical shape could be serious as shells are sensitive to buckling due to the initial roughness effect."

"Shells were seldom the most economical way of covering a large space, especially when compared to lightweight tension membranes. ...[F]ormwork has always been a major cost factor."

"There are... new materials such as fibercrete concrete and fiber reinforced polymer (FRP) composites that may be used in shells."

"When designed properly, [shells] are among the most beautiful and efficient of architectural structures. They will present both problems to be solved and opportunities to create for those who take the time to understand them."

"This is a Manual on low cost, permanent shelter for needy families built using unskilled labor."

"This construction is a means of fighting poverty. The work can unite war torn communities, and communities disoriented by natural disaster."

"Thin shell latex concrete shell roofs are one answer to low cost construction of immediate shelter of displaced people groups. liquid and are generally available in... regions where poverty and the need for housing abound."

"An LC HP shell is an HP shell made of latex concrete. Latex concrete is fiberglass fabric stretched over a large frame... and the resulting fabric surface is then saturated with first a slurry of latex and Portland cement (a liquid paste), then when that dries, a ¼ to ⅜ inch thick layer (or layers) of latex concrete made of latex liquid, Portland cement, and dry sand is broomed on."

"The latex concrete is typically made by mixing Portland cement with dry sand to a 1 to 3 ratio by weight, then adding latex liquid until you get a broomable mix."

"Latex liquids are a mixture of polymer latex solids suspended in water... typically at a mix of about 50 percent solids to 50 percent water by weight. This material is then used by manufacturers of construction liquids such as latex paints and cement additives by adding additional water, coloring, and special chemicals such as antifoaming agents. ...[T]rade named materials ...all have properties in common. They improve mechanical strength and adhesion properties, and impart the ability of the concrete to air cure. They remain stable in Portland cement, and resist the penetration of water, hence provide ...good freeze-thaw resistance, and low moisture penetration. They can readily bond with themselves. Latex paints are typically... 20 percent solids by weight... [cement additives] are... about 47 percent solids."

"The strength of latex concrete is [negatively] affected by excess water in the mix. For that reason it is best to work with dry sand. ...[I]f you add the latex to wet sand, you will be watering down what latex you have, and not getting the advantageous physical properties ...Use dry sand. ...Try for a ratio of polymer solids to cement by weight of 0.12 to 0.15, and a water to cement ratio by weight of 0.35 to 0.38."

"The construction of thin concrete shells ended abruptly at the end of the 1970s, mainly caused by the high costs... However, uncertainties in the structural behaviour of shells did not help either. Contemporary progress in finite element software discards these uncertainties as it allows the engineer to closely approach the actual behaviour of thin concrete shells by performing geometrically and physically nonlinear finite element analyses. ...The combination of advanced finite element analyses and ultra high performance fibre reinforced concrete may lead to shells with even greater spans and thinner thicknesses than achieved so far."

"Shell structures have been constructed since ancient times. The Pantheon in Rome and the in Istanbul are well-known examples. After the Roman times the traditions of domes continued up to the 17th century. Since then they seemed forgotten. Stimulated by the newly developed reinforced concrete and the demand to cover long-spans economically and column free the shell made a comeback in the early 20th century. and Ulrich Finsterwalder designed in 1925 the first thin concrete shell of the modern era, the Zeiss planetarium in Germany. The modern era of shell construction is recognised by the trend towards greater spans and thinner shells. Guided by well-known engineers as , Eduardo Torroja, Anton Tedesko, Nicolas Esquillan, and a blooming period of widespread shell construction took place between 1950 and 1970. Shell construction suddenly vanished at the end of the 1970s, mainly caused by the high costs [relative] to other structural systems. Moreover, inflexible usability and uncertainties in the structural behaviour of shells and difficulty of proper analysis methods did not help[,] neither did the stylistic identification with the 1950s and 1960s. Today the great era of thin shells is over, however, nowadays natural free-form shapes and blobs attract more and more attention. In addition, recent developments in concrete technology have led to ultra high performance fibre reinforced concrete with revolutionary performance in tension and compression. Eventually this may lead to a revival of the thin concrete shell."

"In case of a failure, the shell may fail due to large deformations (buckling) or due to material nonlinearity (cracking and crushing) or by a combination of both (so-called inelastic or plastic buckling). ... Opposite to columns and plates, shells experience a sudden decrease in load carrying capacity after the bifurcation point (which can be obtained by a simple linear buckling analysis). ...compound buckling ...refers to several buckling modes associated with the same critical load. In the postbuckling range the modes... start to interact resulting in a significantly reduced load carrying capacity. As discovered by Koiter... geometrical imperfections in the shell cause the bifurcation point never to be reached and lead to... buckling at a considerably lower load. The size of the imperfections determines the limit load at which the shell fails. In case of plastic buckling, the fall-back is further intensified by material nonlinearity."

"[T]wo primary research questions can be formulated: [1] What is for a shell of hemispherical geometry, with given material properties, given support conditions, and subjected to a given load, the knock-down factor which indicates the difference between the linear critical buckling load and the actual critical buckling load taking into account imperfections and geometrical and physical nonlinearities? ...[2] Can high strength fibre reinforced concrete add to the trend towards greater spans and thinner shells with possibilities for even more slender structures? To obtain an answer to the research questions a series of analyses (linear elastic, stability, geometrically nonlinear and geometrically and phy sically nonlinear) is performed on a given hemispherical shell: the Zeiss planetarium shell."

"In the early twentieth century was a new building technology. Its novelty inspired experimentation, both from architects, such as Le Corbusier, and from engineers, who dreamed up different applications for the new ferroconcrete. One application for reinforced concrete that developed rapidly was its use in thin shells. These shells spanned great distances or stretched out in dramatic s, their thinness seemingly impossible for the distance they extended. This technology quickly grew ever more common, especially in long-span utilitarian settings, where thin shell concrete was able to cover large areas economically."

"The German engineering firm of ['s]... design of the concrete dome for ’s Century [or Centennial] Hall in Breslau... in 1913... became the first modern building whose clear span exceeded Rome’s Pantheon. Other notable structures of this early phase are the elegant works of Eduardo Torroja in Spain, including the Algecira market hall (1934), and Freyssinet’s economical segmented system for an aircraft hangar at Orly (1921)."

"By the 1970s the use of thin shell concrete had all but disappeared... This change was due to a combination of [economic] factors... This disappearance was also caused by the design challenges [of] thin shell concrete. Shell structures, because of their thinness, must be shaped to conform to the forces present in the structure. Until recently this shell form-finding could only be done... with specialized computer expertise, or through... physical model testing and measurement. ...In recent years ...simple computational models ...have been adopted ...to explore rapid form-finding in ...early design phase."

"Forces present in the structure, shape thin shell concrete. Areas of uniform load present smooth, catenary curvatures, while areas of concentrated force express themselves as sharp bends or spikes in the surface form."

"By their very nature all funicular structures, including thin shell, use... less material... By designing only for pure tension or compression these structures experience very little force. These pure forces require less material to resist..."

"Dieste’s hypar masonry roofs are inexpensive, utilitarian statements about space enclosure..."

"[T]he second wave of shell building (1940-1960s)... focused almost exclusively on s... [to] include s and hyperbolic paraboloids. ...[T]hey were definable through mathematical formulas, which allowed the designer to understand the forces... Ruled surfaces are... more constructible, because they can be created out of linear elements, such as... boards and pipes..."

"The most prominent designer to eschew s is the Swiss engineer . In 1954... Isler hit on the idea that a “bubble” (in this case a pillow) takes the optimal shape for its edge boundaries. Isler began to construct models by inflating surfaces or by hanging and then hardening them."

"I have selected the use of hanging models to simulate compressive forces. This is one of the longest-used form finding techniques. It has its roots in physical models, but in recent years it has also given rise to a range of digital tools that are fairly accessible to an uninitiated designer... Hanging models... can be used to simulate... funicular structures. ...derived from the Latin word for “rope”... a structure takes its shape in response to the magnitude and location of forces acting upon it. For example, a rope suspended from two level points will form a “V” when a single point load is added at midpoint, but will form a catenary when under an evenly-distributed load. While a suspended rope is a purely tensile system, if inverted and made rigid that same form converts into a system that is in pure compression. This was first postulated (and wonderfully expressed) by the English scientist Robert Hooke... The value of a structure that is purely in compression is that it experiences no due to structural loads. With no bending present materials can be used very efficiently, allowing for the use of extremely thin elements... materials that are strong in compression... as tiles or masonry, can... be employed."

"History shows that not all thin shell concrete buildings are funicular—other families... chosen for pragmatic reasons such as their constructability, or because they were geometrically simple enough [that] through calculation... bending... was [found to be] within... tolerances... for the material."

"[T]he infill fields of a Gothic cathedral’s ing behave as masonry shells, and by the 1860s masonry s of great beauty were developed by in both Spain and the United States. Gustavino’s work and graphic design methods... influence[d] Antonio Gaudí... whose work has been shaped by an interest in force-derived architectural form. While early engineers such as Guastavino pushed unreinforced masonry’s limits in thin shell construction, it was the introduction of steel reinforcement, initially in concrete, that sparked the Twentieth century’s interest in thin shell construction. Early [twentieth century] shell-builders were often engineers, and were engaged to design economical long-span structures... as aircraft hangars, train sheds and factories."

"[A] list of factors combined to make thin shell concrete a less desirable solution for long spans by the 1970s. ...material efficiency could no longer off set the labor premiums demanded by complex formworks ...shapes were more difficult to create when an insulating layer was required ...A third challenge posed to compressive structures ...was the rapid development of s. ’s experiments with tensile membranes were mature enough in 1972 that they were used on Munich’s Olympic Stadium."

"Shells play a special, singular role for engineers. Their shape directly derives from their flow of forces, and defines their load-bearing behaviour and lightness, saving material by creating local employment, their social aspect. This is especially true for thin concrete shells with their characteristic curvatures: single curvature (cylindrical and conical), synclastic (dome-like), anticlastic (saddle-like) of free (experimental). If well formed, there are no bending but membrane forces only (axial compression and tension)..."

"The shell designer seeks forms to carry the applied loads in axial compression with minimal bending forces. The earliest example of structural form finding for an arch was published by the English engineer and scientist, Robert Hooke... 1676... As hangs the flexible line, so but inverted will stand the rigid arch. ...'Hooke's law of inversion', can be extended... and considered for shell structures of various geometries. In the context of shell structures, the term funicular means 'tension-only' or 'compression-only' for a given loading, typically considered... Unlike the case of the hanging cable with a single funicular form... hanging membranes have multiple possible forms. ...[T]he three dimensional shell can carry a wide range of different loadings through membrane behaviour without introducing bending. ...[A] three-dimensional model of intersecting chains could be... used to design a design a discrete shell, in which elements are connected at nodes, or the model could be used to help define a continuous surface. If hanging from a circular support, the model-builder could create a network of meridional chains and hoop chains. By adjusting the length of each chain, various tension-only solutions can be found... Once inverted, this geometry would represent a compression-only form. Such... would quickly illustrate that many different shell geometries can function in compression due to self-weight."

"Today, most engineers fear shells and domes: they are mysterious and difficult to assess and master. ...Historic arches, shells and vaults are too easily seen as risks instead of opportunities. Under the motto of 'safety', these structures are destroyed and replaced by common beam-column systems. This is regrettable: their great historic and aesthetical value is lost forever. A better understanding and assessment of their structural behaviour holds the key to their conservation. ...[S]hells and arches are highly efficient structures."

"A collander... contains holes for draining food, but these holes do not stop it from being a shell. A sieve... is made from a large number of initially straight wires which are woven into a flat sheet and then bent into a hemisphere. It is also a shell, a gridshell. ...The spider web is essentially flat and made up of straight elements and when the wind blows, it bows outward like a sail and becomes curved. ...We call this a 'form-active' structure. This feature is characteristic of tension structures. The sieve may be in tension, compression, or a mixture of the two, but appears rigid. It does not significantly adjust its shape to the applied loading and, therefore, we call this a 'form-passive' structure. Where it is in compression, deflections lead to a structure becoming less able to carry the load, possibly leading to buckling. Columns carry loads via axial forces, but bending stiffness is required to stop buckling, and so it is with shells, although with shells buckling is resisted by a combination of bending and in-plane action."

"The hyperbolic s are associated with nuclear and thermal power plants... they are also used... in some large chemical and other industrial plants. [T]hey are high rise structures in the form of doubly curved thin walled shells of complex geometry..."

"The... structure is made of high-strength Reinforced Cement Concrete (RCC) in the form of hyperbolic [thin shell standing on diagonal, meridional, or vertical supporting columns and radial supports. The shell is sufficiently stiffened by upper and lower edge members."

"The hyperbolic form of thin-walled towers provides optimum conditions for good aerodynamics, strength, and stability."

"[T]he first cooling tower shell [to be] analyzed by means of a shell bending theory [was in 1967]. ...Because of the complex geometry of the cooling towers and also the classical methods of analysis of shell structures, the most preferred method of the modeling and analysis of NDCT [natural draft cooling towers] is [the] (FEM)."

"Deformation response and ultimate strength of RC shell structures are governed predominantly by material response of concrete and reinforcing steel, tensile cracking of concrete, [and] bond between concrete and steel.... Softening response of concrete due to quasi-brittle cracking in tension also... influences the nonlinear response by inducing loss of strength and stiffness... Due to all [of] these, analysis requires attention for realistic modeling of the layer of shell concrete confined between the reinforcement layers. ...[O]ne of the most challenging areas... is the modeling techniques using the layered elements."

"The NDCT [natural draft cooling tower] shell structures are submitted to environmental loads such as wind, earthquake and thermal gradients that are in nature. The dead loads, settlement, and construction load are... common... and various accidental loads, e.g., explosion [are]... experience[d]... in their lifetime."

"The meridional directed forces developed in [a] tower shell due to the self-weight... may cause local (diamond-shaped) buckling or axisymmetric circular buckling... Overall buckling of the tower shell may [be] caused by combination[s] of wind load and self-weight..."

"[I]n 1967, closed-form expressions [were] derived by Gould and Lee... for determining the resultant stresses in the shell and corresponding deformations under static seismic design load."

"[A c]ooling tower is normally designed for stagnant ambient air condition, but experimental observation showed that cooling efficiency... might decrease to 75 percent in the range of moderate to high wind velocity..."

"Experimental and numerical observations identically showed that heat transfer capacity of the cooling tower proportionally increased with wind velocity up to 3 m/s, and then decreased for higher wind velocity..."

"Concrete shell structures, often referred to as ’thin shells’ are suitable structural elements for building spacious infrastructures. ...Loads acting on the surface of shell structures are mainly carried by the so called membrane action. This is a general state of stress [which] consists of the in-plane normal and resultants only. In comparison, other structural forms such as beams and plates carry loads acting on their surfaces by action, which can be said [to be] structurally less efficient. Usually the in-plane stresses in shells are low such that with a relatively small thickness it is possible to span over large distances."

"Compared to structural elements such as beams, slab and walls, the structural behaviour of shells in not easy to predict. Hence evaluating the accuracy of the results obtained from FEA of shell structures is a challenging task. Having the knowledge and understanding of the analytical solution method can provide the basis for this verification and... give ...much needed insight into the structural behaviour of shells. ...for some of the most commonly constructed concrete shell structures, a complete analytical solution procedure is available. The two types of concrete shell structures considered in this paper are axisymmetric shells and cylindrical shell roofs. ...[A]xissymetrical shells include structures such as containment buildings, tanks and silos. ...[C]ylindrical shell roofs are often preferred structural elements for large span concrete roof structures."

"A shell can be defined as a body that is bounded by two surfaces parallel to its middle surface, and is deformed in any arbitrary manner. This is true for shells of a constant thickness... considered in this study. ...One particular way of classifying shell surfaces is according to their Gaussian curvature. \kappa_g = \kappa_1 \cdot \kappa_2 = \frac{1}{r_1} \cdot \frac{1}{r_2}Another way of describing shell surfaces is according to how the surfaces are generated. Using this method, in 1980 classified shell surfaces into Geometric, Structural and Sculptural surfaces. Geometric shells are well defined mathematically and... easily calculated analytically. These type of shells were quite significant in the development of shell structures [when] computer[s]... were not available. ...geometrically shell surfaces can be classified as cylindrical... spherical... conical... paraboloidal... etc."

"[C]losed surfaces are more rigid than open surfaces. ...Therefore to achieve ...rigidity the openings [are] compensated."

"[U]sing concrete shells as roofing provides the possibility of constructing spacious columnless buildings... has enhanced this possibility."

"Concrete shells can be built by the assembly of several cast units, or cast in one piece (monolithic). Monolithic concrete shells are structurally stronger..."

"[D]evelopment of the theory employs (elastic material), equilibrium and compatibility. Hooke’s law relates strains with stresses, equilibrium relates stress resultants with external loading and compatibility relates strains with deformation/displacements. These three sets of equations together with appropriate boundary conditions make up the mathematical aspect of the problem."

"[T]he ratio [of] radii of curvature to thickness of the shell, \frac{R}{t}... greater than 20 can be characterized as thin shells... an egg shell has a ratio of around 55..."

"[W]e will mainly be dealing with uniform shells. The shells are uniform in the sense that the material properties do not vary through the thickness. (RC) is... regarded as sufficiently uniform... [since] the difference in between steel and concrete is not large..."

"The greatest of them all, in my opinion was Nervi. ...First of all, he did a tremendous volume of work. Now Torroja, from Spain, was very good, but the bulk of his work was quite small. ...Candela came along and... was very experimental and very creative, but he stuck almost entirely with the hyperbolic paraboloid form of the shells. ...[H]e did... a lot of great buildings, but they were... limited in that they were all this one type... Nervi stuck with all kinds of different stuff: precast... and Nervi had a laboratory in ... where he made experimental models. ...Torroja had a lab too and... finally became... just a professor... [so he] didn't do a great deal of volume. ...Nervi kept on doing these things his whole life... working with models, and working with whatever theory he could learn... [T]he great Lamella roof hangar he built before the war, that the Germans finally blew up when they had to retreat from Italy, was a magnificent... and a huge structure... [T]he other two... Torroja and Candela, were excellent engineers. Candela became a friend of mine later on... but they never had the tremendous variety and the huge buildings that Nervi did... Nervi's the guy that I really admire... most..."

"The first shell I did was in Honalulu, and there I worked with an architect, that I had worked with at the Navy yard, named Pete Wimberly... Wimberly's architectural firm went on to be one of the biggest in the world. ...Pete and I were good friends, and when I went to Honolulu I'd stay in his house, and we'd start barnstorming at night. ...A lot of our stuff was just crazy talk, but a lot of it was freeing ourselves of inhibitions that later on we remembered... Pete had a very good intuitive sense for structure. He could... guess a structure that would make sense. ...[T]he first shell I did was a bowling alley near Pearl Harbor... a single curvature shell, cylindrical shapes... a span of about 93 feet... I could not find any way that... other shells were engineered. If you tried... you'd always get some kind of double-talk... [T]he world didn't have translations of everything then, like it has now. If a guy did something behind the it stayed... [T]he way I finally did it, I figured out that it must behave an awful lot like a... simple beam, even though it was a... curved structure, and so largely I figured it that way and it worked fine, and it's still up, and it was quite thin, it was 2 1/2 inches thick. In that day that was pretty daring..."

"Now what got me into shells... was a building in South America... and it absolutely enchanted me. It was in ... a baseball stadium... doubly curved... I saw this thing, and all I'd ever known... the buildings that were being built in those days were boxes, very uninspired things, and here I see this picture, this gorgeous shell... and it just enchanted me. I thought, "My God, what a beautiful structure, but how on earth does it stand up? How did the guy do it?" ..[T]hat is what really made me decide, "I've got to get the answer to this. How is this done?" [T]hat's what set me off on years and years of searching before I finally found a way to do it. ...[W]hen I finally did a building... I searched around into the theory of shells until I understood the theory... [T]hen I started looking for ways of solving these things, and I found out that they did not exist in the... architectural structural engineering profession... [F]ortunately at that time... we had here a very huge aerospace industry, and I had friends at Lockheed... I got in touch with a guy at Lockheed... and they had ways of solving very difficult problems because they were building the rockets... and so I found this way of doing it... [I]t was a very tedious, complex way of doing it, but you would get an actual, true answer... [I]t was done... the same way that it's done today with computers... But you could do it my way... You took two guys... I was one of them... they go through it step by step, and then [periodically]... compare the answer... to make sure that they don't go off. ...You could get an answer. You don't get it down to the forth of fifth decimal... The smallest I could get, chunks of the shell to work with, would be about [a theoretical] 2 feet square... Today, with a computer, you can get down to 2/10 of an inch... But it was such a tedious, horrible way of working that I never used the system again. By then I learned enough that I knew ways of short-cutting that were not as accurate... but that were close enough... [B]y this time I had developed a pretty good feel... and so I'd cut shells in pieces in my mind, put them back together again, and put them in equilibrium... From this, I finally found my way of doing things. ...As far as I know, nobody had ever done it that way... They'd done aerospace stuff this way... but there they'd put ten guys on it, not two. ...Several times I did things that I thought were the first, but I just said that "It's not universally used, or known..." or something like that. ...You're doing something that you're not really aware of yourself, which is, you're developing a very sophisticated, intuitive way of working with these things, where you can just... take them and you can say it doesn't look right... which was the way architecture was done all through the Middle Ages... in fact, in Antiquity... they didn't have engineers, all they had were architects."

"Looking back to the past century, there were various visionary designers such as Isler, Otto, Candela and Shukhov using design methods comparable to today’s computational design, operating in a pre-computational parametric set-up. They applied mathematical algorithms and principles observed in nature to develop pioneering buildings... as milestones of architectural production. Vladimir Shukhov... was one of the first to embrace such an innovative approach."

"One of Shukhov’s most significant architectural inventions was the thin metal lattice (or ' shell') structure. This was developed after intense research into the most rational type of rafters which weighed and cost the least and which could be assembled quickly. Shukhov suggested a formula to define the proportional relationships between structural elements, which at first sight seemed senseless:α = e = c'where a- length of panels, e - minimal distance between frames, and с - distance between two purlins, dependent on the actual situation"

"According to the formula, the minimal covering weight could be achieved only if the construction had no s and if the distance between es was equal to the distance between the missing purlins. The answer to this riddle was the spatial lattice structure, where trusses and purlins were the same, and the distances between trusses and purlins were equal. In 1895 Shukhov obtained a patent for the invention. The new structures were first presented to the general public at the All-Russian Industrial Art Exhibition in Nizhniy Novgorod in 1896... where Shukhov designed a number of objects using three types of lattice structure: suspension, vaulted and rigid spatial shell."

"Suspension lattice structures... were based on tension, the most advantageous type of stress for metal constructions... designed according to Shukhov’s elaborate investigations of material properties. ...They were called ‘roofs without trusses’... and the clear, extremely simple suspension structure system and the easy-to-perform node conjunction made on-site construction fast and straightforward."

"Shukhov’s lattice-suspended and vaulted structures represented a carrying surface, which could be shaped in any form. ...The density of the grid made it possible to attach it to the shell without additional structures. ...[T]he grids were two to three times lighter than roofs with conventional frames..."

"In 2010, the journal Detail published an analysis of Shukhov’s constructions, calling his approach to design 'an early example of ’..."

"Galankin... writes that Shukhov used to make calculations in a unique way... so laconic... that other specialists found them difficult to understand. In spite their brevity... if Shukhov was asked about load, rod stress, rod profile and section, rivet quantity, material weight, temperature impact or any other specifications, he always had an answer, because his concise calculations covered all these aspects, but nothing that was irrelevant..."

"And Jacob rose up early in the morning, and took the stone that he had put for his pillows, and set it up for a pillar, and poured oil upon the top of it. And he called the name of that place Beth–el: but the name of that city was called Luz at the first: that is, The house of God. And Jacob vowed a vow, saying, If God will be with me, and will keep me in this way that I go, and will give me bread to eat, and raiment to put on, So that I come again to my father's house in peace; then shall the Lord be my God: And this stone, which I have set for a pillar, shall be God's house: and of all that thou shalt give me I will surely give the tenth unto thee."

"Like all great churches, that are not mere store-houses of theology, Chartres expressed, besides whatever else it meant, an emotion, the deepest man ever felt,— the struggle of his own littleness to grasp the infinite. You may, if you like, figure in it a mathematic formula of infinity,— the broken arch, our finite idea of space; the spire, pointing, with its converging lines, to Unity beyond space; the sleepless, restless thrust of the vaults, telling the unsatisfied, incomplete, overstrained effort of man to rival the energy, intelligence and purpose of God. Thomas Aquinas and the schoolmen tried to put it in words, but their church is another chapter. In act, all man's work ends there;— mathematics, physics, chemistry, dynamics, optics, every sort of machinery science may invent,— to this favor come at last, as religion and philosophy did before science was born."

"...we must go to the poets to see what they all meant by it; but the sum is an emotion — clear and strong as love and much clearer than logic,— whose charm lies in its unstable balance. The Transition is the equilibrium between the Love of God,— which is Faith, and the Logic of God,— which is Reason; between the round arch and the pointed. One may not be sure which pleases most, but one need not be harsh towards people who think that the moment of balance is exquisite. The last and highest moment is seen at Chartres where, in 1200, the charm depends on the constant doubt whether emotion or science is uppermost."

"Granted a Church, Saint Thomas's Church was the most expressive that man has made, and the great gothic Cathedrals were its most complete expression. Perhaps the best proof of it is their apparent instability. Of all the elaborate symbolism which has been suggested for the gothic Cathedral, the most vital and most perfect may be that the slender nervure, the springing motion of the broken arch, the leap downwards of the flying buttress,— the visible effort to throw off a visible strain,— never let us forget that Faith alone supports it, and that, if Faith fails, Heaven is lost. The equilibrium is visibly delicate beyond the line of safety; danger lurks in every stone. The peril of the heavy tower, of the restless vault, of the vagrant buttress; the uncertainty of logic, the inequalities of the syllogism, the irregularities of the mental mirror,— all these haunting nightmares of the Church are expressed as strongly by the gothic Cathedral as though it had been the cry of human suffering, and as no emotion had ever been expressed before or is likely to find expression again. The delight of its aspirations is flung up to the sky. The pathos of its self-distrust and anguish of doubt, is buried in the earth as its last secret. You can read out of it whatever else pleases your youth and confidence; to me, this is all."

"Gaudí was drawn not just to the aesthetics of the catenary but also to what it represented mathematically. His use of catenaries made the structural mechanics of a building a principal feature of its design. Gaudí realized that the entire architecture of a building could be drafted using a model of hanging chains... when he was commissioned to design a church the Colònia Güell... he made an upside-down skeleton of the project. Instead of using metal chains, he used string weighed down by hundreds of sachets containing lead shot. The weight of each sachet on the string created a mesh of 'transformed' catenary curves. The arches of these transformed catenaries were the most stable curves to withstand a corresponding weight at the same position (such as the roof, or building materials)."

"Why do you speak to me of the stones? It is only the arch that matters to me." Polo answers: "Without stones there is no arch."

"Wherefore a monk's whole attention should thus be fixed on one point, and the rise and circle of all his thoughts be vigorously restricted to it; viz., to the recollection of God, as when a man, who is anxious to raise on high a vault of a round arch, must constantly draw a line round from its exact centre, and in accordance with the sure standard it gives discover by the laws of building all the evenness and roundness required...."

"Centres, or centre-pieces of wood, are put by builders under an arch of stone while it is in the process of construction till the key-stone is put in. Just such is the use Satan makes of pleasures to construct evil habits upon; the pleasure lasts till the habit is fully formed; but that done, the habit may stand eternal. The pleasures are sent for firewood, and the hell begins in this life."

"Within a shed erected on the construction site of the church of the Sagrada family... Gaudí... made an upside-down model using lightweight cables to represent the structural lines of the future church—a model based on the structural notion of the inverted catenary. ...Analogically represented by little pouches filled with lead pellets the action of the stresses has been done ...The resulting chain configurations are used to determine the geometrical shapes and structural profiles of columns, pillars, arches, and vaults. ...Vicens Vilarrubias i Valls took photos of the model ...Gaudí used these photos upside-down to draw over them the external and internal elevations, studies of details and sections of the building."

"The exact shape of funicular (sometimes called linear or theoretical) arch[es] that carry all applied loads by axial compression only, may be developed by the same methods as used for finding the shape of cables. ...If the actual shape of the arch is different from funicular shape, the bending moment at any section of an arch is proportional to the ordinate or intercept between the given arch and funicular arch... This principle is called Eddy's Theorem."

"Corol. 6.—In a vertical plane, but in an inverted situation, the chain will preserve its figure without falling, and therefore will constitute a very thin arch or fornix: that is, infinitely small, rigid, polished spheres, disposed in an inverted curve of a catenaria, will form an arch no part of which will be thrust outwards or inwards by other parts, but, the lowest parts remaining firm, it will support itself by means of its figure... none but the catenaria is the figure of the true and legitimate arch or fornix. And when the arches of other figures is supported, it is because in their thickness some catenaria is included. ...From Corol. 5... it may be collected, by what force an arch or buttress presses a wall outwardly, to which it is applied. For this is the same with that part of the force sustaining the chain, which draws according to a horizontal direction. For the force which in the chain draws inwards, in an arch equal to the chain drives outwards. All other circumstances, concerning the strength of walls to which arches are applied, may be geometrically determined from this theory, which are the chief things in the construction of edifices."

"From all ages architects have made use of arches in public buildings, as well for strength as beauty. Yet what was the true geometrical figure of an arch was not known before my demonstrations came out."

"It was comparatively late that the theory of arches attracted the notice of mathematicians. Dr. Hooke gave the hint, that the figure of a perfectly flexible cord or chain, suspended from two points, was the proper form for an arch. Galileo considered the catenary as a parabolic curve, and John Bernouilli appears to have been the first who discovered its nature. Dr. Gregory (Phil. Trans. 1697) published an investigation of its properties, and observes that the inverted catenary is the best form for an arch on account of its lightness. This is true so long as it is not pressed by an extraneous weight. It is not, however, capable of bearing a load on any part, much less of being filled up on the spandrels, which must be the case in practice. Other considerations must be involved before it can be fitted to receive a roadway or other weight, either upon its crown or haunches."

"The flexible chain, hanging under the action of applied force, will assume a certain shape, namely the catenary if the chain is subjected only to its own weight, or a if the load is uniformly distributed horizontally. Whatever the load, there will be a corresponding shape, and the structural action in all cases is the same; purely tensile forces are transmitted along the centre line of the chain. As Hooke saw in 1675 with his ut pendet continuum flexile, sic stabit contiguum rigidum inversum, ...a hanging chain may be inverted to give a satisfactory arch to carry the same loads, but working in compression rather than tension. The compressive arch, however, if of vanishingly small thickness, would be in unstable equilibrium, and stability is conferred in practice by making the arch ring of finite depth. Now if purely compressive forces, without bending, are to be transmitted from one portion of the arch to the next (as purely tensile forces are transmitted in the chain), then the arch centre line can accept only a single type of loading. Thus a parabolic arch can carry only a uniformly distributed horizontal load (although the magnitude of the load is arbitrary). It is the depth in a real arch which enables the arch to carry wider ranges of loading; a large number of different idealized centre-line arches can be contained within a given practical profile. ...[T]his must be so, or no mediaeval bridge would have survived its decentering."

"The true Mathematical and Mechanical Form of all manner of es for building with the true butment necessary to each of them, a Problem which no Architectonick Writer hath ever yet attempted, much less perform'd. ...Ut pendet continaum flexile, sic stabit contiguum rigidum, which is the Linea Catenaria."

"History fades into fable; fact becomes clouded with doubt and controversy; the inscription moulders from the tablet: the statue falls from the pedestal. Columns, arches, pyramids, what are they but heaps of sand; and their epitaphs, but characters written in the dust?"

"I will begin with the subject of your bridge... and it is with great pleasure that I learn... that the execution of the arch of experiment exceeds your expectations. ...You hesitate between the catenary and portion of a circle. I have lately received from Italy a treatise on the equilibrium of arches, by the Abbé Mascheroni. It appears to be a very scientifical work. I have not yet had time to engage in it; but I find that the conclusions of his demonstrations are, that every part of the catenary is in perfect equilibrium. ...I would propose that you make your middle rail an exact catenary, and the interior and exterior rails parallels to that. It is true, they will not be exact catenaries, but they will depart very little from it; much less than portions of circles will."

"He talked to her endlessly about his love of horizontals: how they, the great levels of sky and land in , meant to him the eternality of the will, just as the bowed Norman arches of the church, repeating themselves, meant the dogged leaping forward of the persistent human soul, on and on, nobody knows where; in contradiction to the perpendicular lines and to the Gothic arch, which, he said, leapt up at heaven and touched the ecstasy and lost itself in the divine."

"Like two cathedral towers these stately pines Uplift their fretted summits tipped with cones; The arch beneath them is not built with stones, Not Art but Nature traced these lovely lines, And carved this graceful arabasque of vines; No organ but the wind here sighs and moans, No sepulchre conceals a martyr's bones, No marble bishop on his tomb reclines. Enter! the pavement, carpeted with leaves, Gives back a softened echo to thy tread! Listen! the choir is singing; all the birds, In leafy galleries beneath the eaves, Are singing! listen, ere the sound be fled, And learn there may be worship without words."

"There is [a].. type of structural behaviour which is not beam-like, truss-like or frame-like but funicular. ...from the Latin for rope - funis. ...the cable is flexible and can only have internal forces of axial tension. ...a cable is not a frame ...Like any spanning structure it has to carry the overall and s. ...If a cable is loaded with a uniformly distributed load, the cable will take up a parabolic shape. ...the funicular shape for this load pattern. ...Because... cables are in direct tension, if they were turned upside down they would be in direct compression. ...this would not be possible for a cable but if the structure could carry compression then the funicular shape obtained from the hanging cable gives the correct shape for an arch that is in direct compression everywhere. ...the idea of inverting cables to find arch shapes was only stated in 1675 by ...Robert Hooke... G. Poleni in 1748 as part of his investigation into the structural behaviour of the dome at St. Peter's... used a correctly loaded chain to determine the funicular shape... If...the loading changes or the arch is built to the wrong shape and the funicular line moves outside the arch, then the arch will have to maintain its shape by frame action or collapse."

"So counsel'd he, and both together went Into the thickest wood; there soon they chose The fig-tree, not that kind for fruit renowned, But such as at this day to Indians known In Malabar or Decan spreads her arms, Branching so broad and long, that in the ground The bended twigs take root, and daughters grow About the mother tree, a pillar'd shade High overarch'd, and echoing walks between."

"Arches form a distinct class of two-dimensional structural elements that resist external loads through their profile (form). Compared to a beam element of the same span and subjected to the same load, the B.M. in an arch will be much smaller because of the negative B.M. due to the horizontal thrust at the supports (abutments). Graphical solution of arches is much simpler than the analytical solution, and is of adequate accuracy for practical purposes. The solution is based on Eddy's theorem on B.M. in arches and the concept of pressure (thrust) lines. ...In case the structure has the profile of the force polygon, the B.M. at any section will be zero... The structure, in such a case, will be subjected only to axial compression. Such a profile along the length of a beam or frame is known as the pressure line or line of thrust. ...the profile for a given system of forces, which would induce only compressive forces. The profile of a pressure line resembles an arch with linear segments; the profile is sometimes known as a linear arch."

"The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome."

"The arch is one of those brilliant innovations... Spanning... with horizontal beams is a losing game. ...By converting all the stress that fractures the middle of... stone beams—technically tension—into compression on stone piers larger... spaces could be spanned. ...But shift the pressure even slightly off center, and the pillar is likely to collapse. ...In their early incarnations, the limitations of both arch and dome was the ability of craftsmen to shape the stones carefully enough to create blocks precisely in the wedge shapes needed for a particular arch. Despite their mathematical sophistication in most other respects, the architects of antiquity lacked a proper geometric solution to the ideal form of the arch. (It was not until 1675 that the English polymath Robert Hooke described mathematically the shape of an arch loaded in pure compression, that is, with no tension, by showing how it describes an upside-down version of the catenary curve of a hanging chain.) As a result, the only way they could design an arch, and its component stones, was completely by eye, and... such tolerances commanded high prices. Rome overcame this drawback with typical ingenuity, first replacing stones and mortar... and expensive stonecutters with relatively cheap bricklayers. Even more ingeniously, some anonymous Roman builder found how to combine the mortar—in Latin pulvis puteoli—with lime, sand, and gravel to make the first concrete. ...The concrete domes of Rome were not surpassed until the age of steel."

"Certainly the most striking contemporary example of a similar form [ arch] is to be found in St. Louis' ... In its incredible scale and construction out of metal plates this structure also serves as a convenient reminder of the important developments of the production of iron and steel that took place during the Industrial Revolution and that have so significantly affected arches as well as all other types of structural forms for the past 150 years."

"French architects and engineers in the 16th, 17th, and 18th centuries occupied themselves a good deal with roofs with curved ribs, and two systems of constructing the rib were worked out. In the most modern of them, that invented by Colonel Emy, the ribs were constructed of a series of thicknesses of bent timber, one on the back of another, and held together by bolts. In the older system that of Philibert de l'Orme, the ribs were also built up, but the pieces composing them are placed side by side, and either form a polygon approaching a semicircle or are cut to bring them to a curve.&bnsp;thumb|Bourse de commerce (dome of the Paris Corn Market)In fact, the ribs are very much such as... used for the great dome of the Paris Corn Market. There is, however, a great difference between a dome—the strongest of all forms—and one permitting the introduction of as many rings of ties as may be desired; and a roof over an ordinary oblong space, where no such binding together is admissible, and where straight rafters may have to be used, which loads the rib at certain points only. In the latter case, a good many precautions have, generally speaking, to be taken to prevent the rib from being unequally loaded, and so either spreading or losing its shape in some other way. The rib made of unbent timber, side by side, on De l'Orme's plan, is admitted to be stronger than the one made of bent timbers laid one on the back of the other; but both have been largely used, and good examples of both may be met with, even if we confine ourselves to English ones alone, and leave the French ones unnoticed. thumb|Chatsworth - Great Conservatory in the 19th centuryA very fine roof with ribs, one on which the load (though light) is borne without a rafter solely by the rib, is the one erected over the great conservatory built by His Grace the Duke of Devonshire, at Chatsworth. ...It consists of a wide and lofty central portion, with a kind of broad aisle at the sides, roofed at a lower level. The central roof here is of the section of a pointed arch and hipped at both ends, and is entirely covered with glass. It is carried by timber ribs, and the glazing is on the ridge and furrow principle. The low aisle referred to forms to some extent an abutment for the ribs, and the ridge-and-furrow glazing helps, no doubt, to fortify them, but still the greater part of the strength is derived from the ribs themselves."

"All building naturally divides into two classes, the architecture of the beam and that of the arch, which have been called trabeated and arcuated—according to the means which it uses for covering openings and spaces—the first being that which covers them by beams or s, the second that which uses arches. The logical development of the two classes leads in the one to flat ceilings and straight roofs, in the other to vaults and s."

"[A]long with the order, the architecture of Rome had inherited from the Etruscans the arch, despised and rejected by the Greeks... It was probably the child of the bricklayer, who has no other means of bridging an opening; at least we find it first in alluvial Mesopotamia, where the Chaldees, who had no stone to build with, raised their great pyramids and built their palaces of bricks, and where the Assyrian conquerors who appropriated their civilization and art, as the Romans did the Greek, adopted it from them and used it on a great scale. Born in the oriental brick-fields, it came to the Greeks with all the associations of ignoble material, profane uses, and hated sponsors. Every influence of religious association, conservatism, and respect for the Egyptian example, from which they had learned much, bound them to their trabeated style. Still more, the instinct for harmony of form which dominated both Egyptians and Greeks could but warn them that the use of the arch not only implied a change of their constructive system, but was at war with their whole architectural scheme of lines, proportions, and monumental effect. Even as late as the time of , after long subjection of Greece to Roman control, the arcaded conduit to the at Athens seems to show the persistent resistance of Greek workmen on their own soil to the very principle of the arch, for the arches are cut through solid slabs of stone instead of being built up in the fashion of the true arch."

"The recognized leading position of the author in this field of structural design and the extensive use of his system of arch construction in all parts of the world should be sufficient justification for presenting this book... The present work constitutes one of the most thorough treatments of reinforced concrete arches in any language. ...After a brief discussion of the fundamental principles of arches and a simple though comprehensive treatment of the stresses in reinforced concrete sections, there are presented analytic and graphic methods for the complete design of all types of concrete arches occurring in practice. The graphic methods which are given, permitting the use of influence lines, will be found very practical... The effects of temperature, of yielding abutments and of nonvertical loads are separately considered. ...In addition to the exact treatments, simple approximations and short cuts are introduced which will prove highly useful for preliminary and less exacting designs. Easily-applied formula are developed for determining in advance the best curve for an arch and the required dimensions and reinforcement. ...The principle of the Melan system of arch construction is fully explained and its inherent economy concretely demonstrated."

"On the arch strip... we have certain forces acting; usually... forces of gravity... vertical loading. ...the dead weight of the arch and superstructure together with the useful or live load. Now consider the archstrip (Fig 1) divided into separate segments or s by joint-planes or sections 1, 2, 3, ..., with the end planes A and B resting against fixed abutments. With the... assumption of no shears in the head planes, each voussoir, e.g., 1-2, is subjected to the action of three forces, namely, the given external load P2 and the two resultant pressures R1 and R2 in the abutting joints. These forces must hold each other in equilibrium and may therefore be represented by a force triangle 1-2-O; in this way either joint-pressure may be determined when the other is known. Consequently all of the joint-pressures may be found as soon as any one of these forces is given in its magnitude, direction, and point of application. The forces acting at the end planes A and B are the pressures, and their opposing forces are the abutment reactions K1 and K2. The application of these reactions takes the place of the abutments, so that the arch may be considered an independent system in equilibrium under the forces \sum P, K1 and K2."

"The action and reaction between adjacent voussoirs occur along the lines of the forces R, therefore the polygon composed of these forces is appropriately named the Line of Resistance. It may be obtained as the funicular polygon of the forces P with the end-reactions K as the terminal sides."

"[B]uilding stones and concrete exhibit the properties of elasticity, although not so perfectly as to permit a constant ratio between stress and strain... For compression within the limits of safe stress, however, such proportionality may be assumed without any considerable error so that a constant coefficient of elasticity may be used... The theory of the elastic arch may therefore be applied to arches of all classes of masonry, including monolithic arches of concrete, provided no tensile stresses or only very small tensile stresses are allowed to occur. The same theory also forms the basis for the design of reinforced concrete arches..."

"A place you put people... to forget about 'em!"

"Witness if you will a dungeon, made out of mountains, salt flats and sand that stretch to infinity. The dungeon has an inmate: James A. Corry. And this is his residence: a metal shack. An old touring car that squats in the sun and goes nowhere - for there is nowhere to go. For the record let it be known that James A. Corry is a convicted criminal placed in solitary confinement. Confinement in this case stretches as far as the eye can see, because this particular dungeon is on an asteroid nine million miles from the Earth. Now witness if you will a man's mind and body shrivelling in the sun, a man dying of loneliness."

"The final triumph of Indian architecture came under the Moguls. The followers of Mohammed had proved themselves master builders wherever they had carried their arms—at Granada, at Cairo, at Jerusalem, at Baghdad; it was to be expected that this vigorous stock, after establishing itself securely in India, would raise upon the conquered soil mosques as resplendent as Omar’s at Jerusalem, as massive as Hassan’s at Cairo, and as delicate as the Alhambra. It is true that the “Afghan” dynasty used Hindu artisans, copied Hindu themes, and even appropriated the pillars of Hindu temples, for their architectural purposes, and that many mosques were merely Hindu temples rebuilt for Moslem prayer;119 but this natural imitation passed quickly into a style so typically Moorish that one is surprised to find the Taj Mahal in India rather than in Persia, North Africa or Spain."

"The beautiful Kutb-Minar exemplifies the transition. It was part of a mosque begun at Old Delhi by Kutbu-d Din Aibak; it commemorated the victories of that bloody Sultan over the Hindus, and twenty-seven Hindu temples were dismembered to provide material for the mosque and the tower. After withstanding the elements for seven centuries the great minaret—250 feet high, built of fine red sandstone, perfectly proportioned, and crowned on its topmost stages with white marble—is still one of the masterpieces of Indian technology and art. In general the Sultans of Delhi were too busy with killing to have much time for architecture, and such buildings as they have left us are mostly the tombs that they raised during their own lifetime as reminders that even they would die. The best example of these is the mausoleum of Sher Shah at Sasseram, in Bihar; gigantic, solid, masculine, it was the last stage of the more virile Moorish manner before it softened into the architectural jewelry of the Mogul kings."

"Aurangzeb was a misfortune for Mogul and Indian art. Dedicated fanatically to an exclusive religion, he saw in art nothing but idolatry and vanity. Already Shah Jehan had prohibited the erection of Hindu temples; Aurangzeb not only continued the ban, but gave so economical a support to Moslem building that it, too, languished under his reign. Indian art followed him to the grave."

"…the very grandeur of the Mogul buildings is oppressive. Europe has its monuments of sun-kings, its Louvres and its Versailles. But they are part of the development of a country’s spirit; they express the refining of a nation’s sensibility; they add to the common, growing stock. In India these endless mosques and rhetorical mausolea, these great palaces speak only of a personal plunder and for a country with an infinite capacity for being plundered. The Mogul owned everything in his dominions; and this is the message of the Mogul architecture. I know only one building in England with this quality of dead-end personal extravagance…the Blenheim. Imagine England as a country of Blenheims, continually built, destroyed and rebuilt over five hundred years, each a gift of the nation and seldom for services rendered…leaving at the end no vigorous nation…no principle beyond that of personal despotism. The Taj Mahal is exquisite…But in India it is a building wastefully without function; it is only a despot’s monument to a woman, not of India, who bore a child every year for fifteen years. It took twenty-two years to build; and the guide will tell you how many millions it cost."

"Furthermore, we are instructed, when we do come across instances of temple destruction, as in the case of Aurangzeb, we have to be circumspect in inferring what has happened and why.... the early monuments – like the Quwwat-ul-Islam mosque in Delhi – had to be built in ‘great haste’, we are instructed...Proclamation of political power, alone! And what about the religion which insists that religious faith is all, that the political cannot be separated from the religious? And the name: the Quwwat-ul-Islam mosque, the Might of Islam mosque? Of course, that must be taken to be mere genuflection! And notice: ‘available materials were assembled and incorporated’, they ‘clearly came from Hindu sources’ – may be the materials were just lying about; may be the temples had crumbled on their own earlier; may be the Hindus voluntarily broke their temples and donated the materials? No? After all, there is no proof they didn’t! And so, the word ‘plundered’ is repeatedly put within quotation marks! In fact, there is more. The use of such materials – from Hindu temples – for constructing Islamic mosques is part of ‘a process of architectural definition and accommodation by local workmen essential to the further development of a South Asian architecture for Islamic use’. The primary responsibility thus becomes that of those ‘local workmen’ and their ‘accommodation’. Hence, features in the Qutb complex come to ‘demonstrate a creative response by architects and carvers to a new programme’. A mosque that has clearly used materials, including pillars, from Hindu temples, in which undeniably ‘in the fabric of the central dome, a lintel carved with Hindu deities has been turned around so that its images face into the rubble wall’ comes ‘not to fix the rule’. ‘Rather, it stands in contrast to the rapid exploration of collaborative and creative possibilities – architectural, decorative, and synthetic – found in less fortified contexts.’ Conclusions to the contrary have been ‘misevaluations’. We are making the error of ‘seeing salvaged pieces’ – what a good word that, ‘salvaged ’: the pieces were not obtained by breaking down temples; they were lying as rubble and would inevitably have disintegrated with the passage of time; instead they were ‘salvaged ’, and given the honour of becoming part of new, pious buildings – ‘seeing salvaged pieces where healthy collaborative creativity was producing new forms’."

"The Muslim invaders were necessarily impressed by Indian architecture and sculpture, expressing as they do foreign religious emotions in terms of images and emblems. What they saw at Delhi, and the other cities of India, which they attacked, was absolutely foreign to them. Yet when they came to raise their own religious buildings, they were not averse to using the spoils of their temples… The ruthless desecration and makeshift conversion of Indian temples into Mosques has led many scholars to regard Indo-Muslim architecture as nothing more than a local variety of hybrid nature. In point of fact, these early Indian mosques which were compiled from Brahamanical fragments, such as the Deval Masjid at Bodhan near Hyderabad, have no direct bearing on the general development of Mosque architecture in India.… On the other hand the use of the spoils of non-Muslim ruins was a widely recognised feature in early Muslim architecture…"

"Just as later Mughal painting is a harmonious blend of Persian and Indian artistic tradition, so the Indo-Muslim architecture of Delhi and Ajmer is a blend. In the Quwwat al-Islam at Delhi and the Arhai din-ka-Jhopra at Ajmer, existing remains bear unmistakable evidence that they were not merely compilations, but the distinctive, planned works of professional architects…"

"Although constructed of destroyed Hindu temples, the Mosques at Old Delhi and Ajmer once and for all set the fashion to be followed by later mosques in Muslim India…"

"The early formative phase of Indo-Muslim architecture, marked by the adaptation of Hindu, Buddhist or Jaina temples, is illustrated by the oldest Mosques at Delhi, Bengal, Jaunpur, Daulatabad, Patan, etc. In Malwa, also, spoils of Hindu temples were used…"

"Creighton says, ‘It appears to have been the general practice of the Muhammadan conquerors of India, to destroy all the temples of the idolaters, and to raise Mosque out of their ruins.’ The statement is of course a gross exaggeration, for innumerable contemporary Hindu and Buddhist temples still exist in the cities of India once conquered by the Muslims. ‘Abid ‘Ali seems to have carried the observation of Creighton further when he remarks, ‘It seems to the writer that the builder of the Mosque [Chhoto Sona Masjid at Gaud] had collected the stones containing the figure of the Hindu gods from the citadel of Gaur where temples must have existed in the time of the earlier Hindu kings.’ (...) In the event of a prodigious abundance of Hindu temple building material scattered all over the province, it is difficult to pin-point the provenance of each stray sculptured piece used in the mosques of Gaud and Hazrat Pandua. The existence of any Hindu temple in the citadel or outside Gaud as ‘Abid ‘Ali tells us, is as difficult to prove as to obviate the fact that no material was taken from Devikot or Bannagar in Dinajpur. Contradicting the views of ‘Abid ‘Ali, Stapleton says, ‘On the other hand from Manrique’s statement that in 1641, he saw figures of idols standing in niches surrounded by carved grotesques and leaves in some stone reservoirs in Gaur, it is possible that except during periods of persecution the Muhammadan Kings of Gaur allowed idols and Hindu temples to remain unmolested in their capital.’ Although examples of the use of Hindu material are not scarce, as proved by the discovery of three sculptured figures from Mahisantosh with Muslim ornament on the reverse side, now in the Varendra Research Society Museum, it would be wrong to say after Creighton that all the Hindu temples were desecrated by the Muslims to procure building material… (...) One of the strongest advocates of the Indianized form of Muslim structures is Havell, who is too intolerant to allow any credit to the Muslim builders for the use of radiating arches, domes, minarets, delicate relief works. He maintains that the central mihrab of the Adina Masjid at Hazrat Pandua is so obviously Hindu in design as hardly to require comments. While Havell writes that ‘The image of Vishnu or Surya has trefoil arched canopy, symbolizing the aura’ of the god, of exactly the same type as the outer arch of the mihrab, Beglar says that the Muslims delighted in ‘placing the sanctum of his orthodox cult (in this case the main prayer niche) on the spot, where hated infidel had his sanctum’. Saraswati is even more emphatic on this point when he contends, ‘An examination of the stones used in the construction of the Adina Masjid (one of them bearing a Sanscrit inscription, recording merely a name of Indranath, in the character of the 9th century AD) and those lying about in heaps all round, reveals the fact, which no careful observer can deny, that most of them came from temples that once stood in the vicinity.’ Ilahi Bakhsh, Creighton, Ravenshaw, Buchanan-Hamilton, Westmacott, Beglar, Cunnigham, King, and a host of other historians and archaeologists bear glowing testimony to the utilization of non-muslim materials, but none of them ventured to say that existing temples were dismantled and materials provided for the construction of magnificent monuments in Gaud and Hazrat Pandua..."

"The Indian Museum, Calcutta, as well as the Bangiya Sahitya Parishad Museum, Calcutta, acquired a large number of architectural objects from the ancient sites of Bengal, particularly, Gaud, Hazrat Pandua, Bagerhat, Hughli, Rajshahi, Dinajpur and elsewhere. Besides freshly quarried basalts, a large quantity of locally available building materials was employed by the architects of Gaud, Hazrat Pandua and elsewhere. Ravenshaw’s unwarranted observation that ‘Though it (Hazrat Pandua) cannot boast of such antiquity as Gaud, its remains afford stronger evidence than those of the latter city of its having been constructed mainly from the materials of Hindoo buildings’, has been brushed aside by Westmacott, who thinks that Hazrat Pandua is older than Gaud. One of the strongest advocates of the Indianized form of Muslim structures is Havell, who is too intolerant to allow any credit to the Muslim builders for the use of radiating arches, domes, minarets, delicate relief works. He maintains that the central mihrab of the Adina Masjid (Pl. III) at Hazrat Pandua is so obviously Hindu in design as hardly to require comments. While Havell writes that ‘The image of Vishnu or Surya has trefoil arched canopy, symbolizing the aura’ of the god, of exactly the same type as the outer arch of the mihrab, Beglar says that the Muslims delighted in ‘placing the sanctum of his orthodox cult (in this case the main prayer niche) on the spot, where hated infidel had his sanctum’. Saraswati is even more emphatic on this point when he contends, ‘An examination of the stones used in the construction of the Adina Masjid (one of them bearing a Sanscrit inscription, recording merely a name of Indranath, in the character of the 9th century AD) and those lying about in heaps all round, reveals the fact, which no careful observer can deny, that most of them came from temples that once stood in the vicinity.’ Ilahi Bakhsh, Creighton, Ravenshaw, Buchanan-Hamilton, Westmacott, Beglar, Cunnigham, King, and a host of other historians and archaeologists bear glowing testimony to the utilization of non-muslim materials (Fig. 3b & Pl. V), but none of them ventured to say that existing temples were dismantled and materials provided for the construction of magnificent monuments in Gaud and Hazrat Pandua."

"Creighton drew the sketches of a few Hindu sculptures which were evidently used in the Chhoto Sona Masjid at Gaud. These are the image of Sivani, the consort of Siva, Varahaavatara or Vishnu in the form of a Boar, Brahmani, consort of Brahma. In the British Museum there are a few images of Hindu and Buddhist character, such as the Brahmani, sketched by Creighton, and the seated Buddha figure. The Muslim builders out of sheer expediency felt no scruple to use these fragments in their mosques by concealing the carved sides into the wall and utilizing the flat reverse side of these black basalts for arabesque design in shallow carvings. Piecemeal utilization of Hindu sculptures were also to be seen in the earlier monuments, such as, the Mosque and Tomb of Zafar Khan at Tribeni, the Mosque at Chhoto Pandua, the Adina Masjid at Hazrat Pandua, etc. ... Cunningham found in the pulpit of the Adina Masjid ‘a line of Hindu sculpture of very fine bold execution.’ Innumerable Hindu lintels, pillars, door-jambs, bases, capitals, friezes, fragments of stone carvings, dadoes, etc., have been utilized in such a makeshift style as to render ‘improvisation’ well-nigh impossible. In many cases as observed in the Quwwat al-Islam at Delhi and the Arhai-din-ka-Jhopra Mosque at Ajmer, pillars were inverted, joining the base with capitals, suiting neither pattern nor size. Still there is no denying the fact that Hindu materials were utilized, yet it would be far-fetched to say that existing Hindu temples were dismantled and converted by improvisation into mosques as observed in the early phase of Muslim architecture in Indo-Pak sub-continent. The ritual needs and structural properties of the Hindus and the Muslims are so diametrically opposite as to deter any compromise and, therefore, the early Muslim conquerors of Bengal said their prayer in mosques built out of the fragments of Hindu materials in the same way as their predecessors did at Delhi, Ajmer, Patan, Janupur, Dhar and Mandu, and elsewhere. In the event [absence?] of any complete picture of pre-Muslim Hindu art as practised in Gaud and Hazrat Pandua, it is an exaggeration to hold the view after Saraswati that ‘indeed, every structure of this royal city (Hazrat Pandua) discloses Hindu materials in its composition, thus, disclosing that no earlier monument was spared.”"

"…During the Husain Shahi period the stone cutter’s art was thoroughly practised and perfected, as walls of gates and mosques were adorned with stone, either quarried from Rajmahal hills or obtained from some existing buildings… …The British Museum, London, has in its collection two sculptured pieces from Bengal, namely, the seated Buddha figure (Pl. XLIIa) and the image of Brahmani. Both these images have on their obverse exquisitely carved diaper work of unmistakable Muslim workmanship. The Indian Museum, Calcutta, has a stone slab carved on the one side with the image of Durga, destroying Mahisha or Buffalow-demon, and on the reverse arabesque. The panel consisting of a scalloped arch with a lotus rosette on each of its sides, surrounded by richly foliated devices, is undoubtedly a Muslim work... The Muslim calligraphers did not feel any scruple to utilize fragments of Hindu or Jaina sculpture in carving out beautiful inscriptions in elegant Naskh, Thulth and Tughra, keeping the images inside the wall…"

"“…Delhi was the source of artistic inspiration for all the later provincial schools of Indo-Muslim architecture. Codrington remarks, ‘At Delhi, the Kutb-ul-Islam marks the beginning of Islamic architecture in India.’ This formative phase of Mosque architecture in India began with the random utilization of temple spoils, Hindu architraves, corbelled ceilings, kumbha pillars with hanging bell-and-chain motifs, which were organised to fulfil the needs of congregational prayer. It is said that the columns of twenty-seven Hindu and Jaina temples were utilized in the great Mosque, at Delhi, rightly called the ‘Might of Islam’. It was built by Qutb-al-Din Aybak in AH 587/AD 1191-92 on an ancient pre-Muslim plinth. …Originally there were five domes in the liwan all compiled of Hindu fragments, as is evident from their corbelled interiors…"

"“…To Iletmish we owe some of the finest Muslim works in India. The Arhai din ka-Jhopra began by Qutab al-Din in AD 1198-99, was also completed by him. Tod had said of it that it was ‘one of the most perfect as well as the most ancient monuments of Hindu architecture’, on the evidence of certain four-armed figures to be seen on the pillars… “The Ajmer Mosque resembles the Delhi Mosque in its use of pre-Muslim materials as well as in its courtyard plan, arched screen, columnar liwan and riwags and use of reconstructed Hindu corbelled domes. All these features, except the fragments of Hindu and Jain carvings used in the work are essentially Islamic. The Ajmer Mosque indicates a further improvement in Mosque design… As Sardar puts it, ‘These pillars have a greater height than those at the Kutub, and are more elegant in their sculpture and general appearance than the converted Mosques in Malwa and Ahmedabad.’”419"

"The Jami Masjid of Badaun, also built by Iletmish is one of the largest mosques in India. Following the traditional courtyard plan, it also utilizes Hindu temple pillars. The entrance arches of the gateways leading into the courtyard of the Mosque presumably recall those in the great Mosques at Delhi and Ajmer…"

"It is said that the star-shaped Jaina Temple built in the Chalukya style at Bodhan in the 9th or 10th century was, also, transformed into a Mosque during the reign of Muhammad Tughlaq (AH 726-52/AD 1325-51).… The Mosque of Qutb al-Din Mubarak Khalji at Daulatabad, dated AH 718/AD 1318, is probably the earliest surviving Muslim structure in the Deccan. It is a square, 260 feet each way, assembled into the usual orthodox plan out of destroyed Hindu pillars, brackets, and beams…"

"Like all other provinces of India, the Deccan, also, witnessed the growth of a distinguished school of Muslim architecture. Its early phase is also, characterized by the adaptation of local temples, for the purpose of Muslim congregational prayer, as exemplified by the Deval Mosque of Bodhan in Nizamabad, near Hyderabad, dated AD 1318, which was formerly a Hindu shrine…"

"The oldest of the Mosques in Malwa is the Kamal Maula Masjid which was built in Dhar in AH 803/AD 1400. Both this Mosque and the slightly later Jami or Lat Masjid are clearly adaptations of ruined Hindu temple material… The transfer of the capital from Dhar to Mandu by Dilwar Khan in AH 794/AD 1392, marks a new phase in the development of Mosque architecture in Malwa. The Mosque built by him in C. AH 808/AD 1405-06 is oblong in ground plan, the western side being formed by the liwan. Its roof is supported by Hindu pillars…"

"When the master-builder has taken up the work concerned, he is to re-establish securely any place where the fortification has fallen into ruins. Let him reinforce and also rebuild it."

"My invention shows a new product which helps to replace timber where it is endangered by wetness, as in wood flooring, water containers, plant pots, etc. The new substance consists of a metal net of wire or sticks which are connected or formed like a flexible woven mat. I give this net a form which looks in the best possible way, similar to the articles I want to create. Then I put in hydraulic cement or similar bitumen tar or mix, to fill up the joints."

"[W]elded wire reinforcement (WWR) [was] formerly known as welded wire mesh or fabric. Welded steel wire reinforcement is the predominant form... A grid of orthogonal longitudinal and transverse cold-drawn steel wires is welded together at every wire intersection... The size and spacing of the wires can vary... based on the requirements... Welded wire reinforcement can be epoxy coated or zinc coated (galvanized). ...Plain and deformed welded wire reinforcement is covered in... ASTM A1064... Stainless steel wires are specified according to ASTM A1022... Epoxy-coated WWR... in accordance with ASTM A884... Galvanized WWR... with ASTM A1060... Even plain wire used in welded wire reinforcement has both chemical bond and mechanical bond to the concrete. The mechanical bond results from bearing of the welded cross wires against the concrete in the grid of reinforcement."

"A thin shell is a special kind of vault whose geometry may include many shapes. ...a three-dimensional form made thicker than a membrane, so that it can not only resist tension as membranes do, but also compression. On the other hand, a thin shell is made thinner than a slab, which makes it unable to resist bending, as a slab does. In short, thin shells are structures thicker than membranes, but thinner than slabs. Thin shells are made possible by the use of materials that work well under tension and compression. Masonry has no tensile strength... Only the availability of and made a thin shell possible."

"RECOMMENDATION 6: Ferrocement in Disaster Relief. After fires, floods, droughts, and earthquakes... [t]ransportation is often disrupted... Supplies of bulky conventional building materials may be stranded outside the disaster area, whereas the basic ingredients of ferrocement may be available on the site or easily transported. The versatility of ferrocement also reduces logistical supply problems: wire mesh, cement, sand, and water can be substituted for the metal used for roofing, woods or plastic for shelters and clinics, asphalt for helipads, steel for bridges, and so on. Moreover, most ferrocement structures, though built for an emergency, will last long after the emergency is over. ...[F]errocement could be used at a disaster site for many purposes: Transport facilities, from simple boats to barges, docks, marinas, helipads, and simple floating bridges or short footbridges as well as road repairs. ...Food-storage facilities, quickly designed to local needs and quickly built, to preserve emergency food supplies. ...Emergency shelters such as, for example, the quonset type of roof, which is easy to erect and highly efficient. ..Public health facilities, such as latrines and clinics, built with ferrocement roofs and stucco-type walls of the same wire mesh and mortar. ...[C]adres of ferrocement workers could be trained in emergency applications and the supervision of local laborers at the disaster site."

"[Ferrocement defined:] A thin walled construction, consisting of rich cement mortar with uniformly distributed and closely spaced layers of continuous and relatively small diameter mesh (metallic or other suitable material)."

"The construction method chosen was the inverted wooden mold. For hulls up to 50 feet in length, and for utilizing unskilled labor, this method has been shown to be most efficient. ...The shape and fairness of the hull is first established and checked with the quick and easy-to-build wooden mold. ..The use of air-powered staple guns to fasten mesh and rods to the hull mold is a quick and efficient method and can be performed with unskilled labor. ..Lamination of the concrete skin is eliminated as the mortar is applied from one side only and vibrated through the hull shell reinforcing. ...Sagging of large unsupported areas is avoided. The men work from the outside of the hull and downwards."

"One inch (25 mm), 21 gauge, hexagonal galvanized mesh was used. This mesh was the type manufacturers describe as "reverse twist," galvanized after weaving. Ten layers were applied... Four layers of mesh were stapled to the mold over 4-mil plastic sheathing. Two more layers of mesh were stapled over 1/4-inch (6.4 mm) diameter vertical reinforcing bars which had been stapled on at 6-inch (152 mm) centers. 1/4-inch (6.4 mm) diameter reinforcing bars were then stapled longitudinally over this second layer of mesh. This layer of reinforcing bar was spot-welded to the first layer at approximately every second joint. This second layer of horizontal rods was applied on 3-inch (76 mm) centers. The last four layers of mesh were hogring fastened to the outside of this last layer of rods."

"Clear plastic 4-millimeter sheathing was hand-stapled to the mold for two reasons: ...To stop the moist mortar from falling through the joints and gaps between the wooden battens planking the mold. ...To form a barrier between the wooden mold and the fresh mortar. If no barrier were placed the wood would draw moisture from the new mortar and reduce its final strength."

"The first four layers of mesh were stapled to the mold over the plastic sheeting. Each length of mesh, already folded double, formed two layers. This first layer of mesh strips, 1-1/2 feet (457 mm) wide, was butted together. The second layer of mesh strips was laid out so as to cover the joints where the first layer was butted together, making a total of four layers of mesh."

"The vertical rods were stapled firmly to the hull. An air-powered staple gun was used..."

"Two more layers of mesh were stapled over the mold. Again 1" x 2" (25.4 mm x 51 mm) wide staples were used. The folded mesh was not lapped but just butted."

"The horizontal rods were welded on. Where a rod terminated on the hull it was lapped for six inches (152.4 mm) with another rod and spotwelded. All the rod joints were treated in this same way. The rods were stapled at approximately three-inch (76 mm) centers. Every second intersection of horizontal with vertical rods was spot welded. As there were two layers of mesh between the vertical and horizontal rods, the mesh was faired smooth in this small area. Care was taken not to burn too large a hole in the plastic sheeting where the rod welding took place."

"Wooden plugs of the same diameter as each through-hull fitting were cut out and placed on the mold in the exact position where the future through-hull fitting was to be installed later. These were cut from doweling and made one inch (25.4 mm) deep. A hole was drilled in the center of the doweling to ensure that the plug did not split when nailed to the mold. The mesh was cut away under the plug and trimmed neatly at the edges. Some attempt was made to place the doweling in a position clear of the intersecting rods."

"Starter rods for the stem, webs, bulkheads, bilge stringers, and engine beds were welded in place. These starter rods were placed at approximately six-inch (152 mm) centers. They were six inches (152 mm) long where they extended through the hull. Quarter-inch (6.4 mm) holes were drilled for these... The starter rods were lap-welded to either the vertical rods or the horizontals, depending on their position."

"One-inch (25.4 mm) chain links were welded to the hull reinforcing cage where scuppers were to be placed. These links were aligned and welded in at deck level. ...[E]xposed steel pieces such as scuppers or screeds which require welding... should always be cleaned and protectively coated."

"The last four layers of mesh were stapled to the hull mold. They were laid in the same way as the first layers. The mesh was fastened... as smoothly and as tightly as possible. It was clipped onto the horizontal rods with 3/4-inch (19 mm) hog rings. ...One-half inch (12.7 mm) hog ring staples which do a neater job could not be located ...All edges of the mesh were stapled down tightly so that no stray ends of mesh would penetrate later through the fresh mortar and thus interfere with the plasterers' work... Mesh over the chain link scuppers was clipped away and the ends fastened down neatly."

"The mortar used for the hulls was a mixture of clean, graded silica sand, ...Portland Cement Type II, and drinking-type water. This silica sand, of the grading and particle shape used in high-strength structures... The sand content used was... one 50-pound (22 Kg) bag of coarse grade, one 100-pound (44 Kg) bag of medium grade and one 50-pound (22 Kg) bag of fine grade. To this graded sand was added two 80-pound (31 Kg) bags of Portland Cement Type II and just sufficient water to make the mortar workable into the hull mesh reinforcing. ...There was one plasterer for roughly every 100 square feet (9 m2) ...Retarders or additives were not used. The sun shelters were moved into place ..."

"First a heavy coat was applied all over the hull. Men stationed inside the hull mold began systematically vibrating the mold planking and checking the gaps between the planking for mortar penetration. Once the mortar had all been applied to the satisfaction of the men vibrating and checking, the excess mortar was then scraped back to the mesh. ...A new thin coat was troweled over the hull and allowed to start setting. When it started to set the hull was sponge troweled, the sponge trowel being used in a circular motion to smooth out surface irregularities. As soon as the sponge troweling was finished, the final steel troweling began. This was carried on until the hull surface had set up too hard to be worked on any further, and was as smooth and fair as the plasterers could make it."

"The hulls were steam cured for 24 hours at a temperature of 150°F (66° C). A steam pipe, perforated for its entire length, was placed under the inverted hull and a rubberized canvas steam tent drawn completely over. The temperature was carefully brought up to 150°F (66°C) in a period of four hours. Twenty-four hours were then maintained at this prescribed temperature until, finally, it was allowed to drop slowly to ambient temperature of 85° F (30°C)."

"The hull was left untouched for 18 hours after the plaster finishing work had ceased. This allowed the hull to set-up hard enough for the men to drag the steam tent over it. It is not advisable to start steam curing too soon, as the jets of hot water from the steam pipe may wash some of the mortar off the hull while it is still green. Before steam curing began the wooden screeds were removed from around the hull sheer."

"[These] low cost, easily built, high quality ferrocement roofings... offer an innovative solution to the serious dwelling problem affecting large numbers of people, especially in the marginal urban areas and rural zones of developing countries..."

"Ferrocement was chosen as the material for the proposed roofing because of its physical properties (strength in compression and tension, impact, permeability, etc.) and because it is cheap and easy to build."

"[I]t was decided to develop a type of roofing based on prefabricated sections. ...With the partial results obtained in this stage, another part of the study could be initiated, i.e. to build this same type of element "in situ"... thus providing solutions for situations in which prefabrication is not appropriate..."

"The adaption of ferrocement precast roofings in self-help construction projects... permits the use of standard components which are easily erected without sophisticated equipment."

"The construction of the mold simply consists of making a dome of well compacted earth, covered by a layer of well-finished concrete having a thickness of 8 cm [3.15 inches], with the shape defined by the trusses... used to [shape] the mold."

"The reinforcement consists of two no. 2 bars along the edges, one of them straight and the other one with the necessary bends to provide the handles to lift and fix the dome to the structure. ...[T]wo layers of galvanized chicken wire, guage 22 with a separation of 13 mm are attached to the bars and directly mounted over the mold, one perpendicular to the other. ...[E]nsure a minimum overlap of 5 cm... and... ensure that these are stretched... to achieve the thinnest section possible."

"The mortar used for the mix is made (using a mixture) of normal or ic cement and sand in a proportion of 1:1.5 by volume and with a water-cement ratio of 0.55."

"After a couple of hours, the desired finish is applied (polishing or brushing), with the object of sealing the cracks or faults that may appear on the surface of the dome."

"The curing of the shell is achieved by covering the surface with wet sand for a period of 72 hours."

"An alternative construction method was also developed which did not require the use of any type of mold or form."

"The best solution found was to form a double curvature surface... The curvature does not necessarily follow a pre-determined law, so that it may be checked roughly "with the naked eye"."

"[T]he smaller the thickness of the cover, the better will be its quality, which is why at the time of pouring, the meshes of the wire should be well stretched. Care should be taken that only enough mortar to cover the reinforcement is used."

"One worker on one of the supports... either manually or with a trowel distributes the mortar over the chicken wire... Simultaneously, another worker from within the room... holds the mortar which is applied from the outside with a metal float or trowel in order that the mortar does not fall. Once this operation is completed, the required finish is applied both from the outside and the inside."

"The central part remains [bare wire] and will be completed after 72 hours. ...[T]he worker can [then] climb on the previously cast portion, carrying out the same process ...[S]upport the dome until the mortar has cured in order to avoid deformations caused by the weight of the mortar and to guarantee curvature of the shell."

"As eight of the shells tested failed as a result of the failure of the supporting concrete ties on the walls, it was decided to build samples which were very well reinforced... The ultimate load increased by 1.7 times for these shells..."

"The domes were very easily repaired by replacing the damaged mortar or mesh..."

"[T]he ferrocement roofings are practically waterproof and that they do not need any special treatment."

"[T]o increase the load capacity of the domes and to avoid excessive deformations, it is necessary to provide the best possible anchoring at the edges."

"[A] dome of any shape will amply comply with safety requirements. Because of this it is believed that it is possible to build domes in situ without specifying the shape of the dome, which makes skilled labor unnecessary."

"Chicken wire mesh was recommended because of its ductility. It shows no oxidation problems as it is made with galvanized wire. It has reliable properties and is low in cost."

"The purpose of this book is to match an existing resource with an existing need. The need is shelter... simpler structures... that can be assembled quickly in the wake of a hurricane or flood... that can be built economically in undeveloped countries... that... provides pleasure in the form of self-made personal retreats..."

"This highly specialized, but by no means highly complicated building technique had been almost forgotten after its first use... in the middle of the nineteenth century until it was virtually reinvented in the 1940s by... ."

"Ferrocement is used relatively little in the housing field because it is regarded as a labor-intensive... building technique. ...It is true that considerable labor is required to put together... sand, cement, and wire mesh... However, the elaborate temporary framework which consumes most of the labor in conventional work is often entirely eliminated... Even if we concede that ferrocement is impractical where labor is expensive... its use requires only time, not skill..."

"All ferrocement can be said to be , but all types of reinforced concrete are not ferrocement."

"[F]erroconcrete would be a more accurate term for our material, but that term is already in common use to describe... reinforced concrete work."

"[F]errocement ...uses wire mesh, rather than heavy rods or bars, as the primary part of its metal reinforcement and which uses sand [in a mortar mixture] rather than a mixture of sand and stone ...as the aggregate in its concrete mix. ...The resultant product can be a shell of surprising thinness, durability, resilience, and, when properly shaped, strength."

"The structural effectiveness of any reinforced concrete, including ferrocement, depends on the almost miraculously fortuitous fact (first discovered in 1870 by ) that steel and concrete have close to identical coefficients of expansion, swelling at exactly the same rate when heated, shrinking at exactly the same rate when cooled. Thus they may be permanently bonded together as a single material, utilizing the best structural characteristics of each: steel has the tensile strength... while concrete has the ..."

"Ferrocement... often acts more like steel than like a standard reinforced concrete. Hit with a hammer, it rings like a bell."

"[F]errocement... may eliminate the need for separate layers of waterproofing."

"[A]t the new ... [the] famous sail-shaped roofs (built of conventional reinforced concrete) have been covered with tile-surfaced panels of ferrocement which serve as waterproofing..."

"[B]ecause of its intrinsic hardening process which continues indefinitely, good concrete gets better and better, imperfect concrete (with flaws that invite erosion and corrosion) gets worse and worse."

"[B]efore... crude beginnings of work with conventional reinforced concrete, work with ferrocement had already begun. ...The ferrocement technique seems to have been first used by ... and, apparently... independently, by ...Jean-Louis Lambot. ...Lambot called his invention "ferciment" and used it to build boats... He constructed his first boat in 1848..."

"Although... two of the first patents for reinforced concrete of any type... were for ferrocement, that particular type of reinforced concrete was generally underutilized—in fact, forgotten—until 's work of the 1940s. ...The turning to ferrocement... was based on the logical use of a known fact: the structural behavior of reinforced concrete is most effective near the points of its reinforcement. ...Nervi was first to ask the question... why not distribute the metal reinforcement so evenly that all the concrete is in immediate proximity to it? On this theoretical foundation Nervi performed the experiments which led to his establishment of ferrocement building technique as we know it today."

"[B]y the end of 1943 Nervi's firm was at work on three 150-ton transport boats, their hulls completely of ferrocement, and one 400-ton vessel, largely of ferrocement. The first construction was interrupted by the war, and it was not until 1945 that Nervi's method resulted in... [t]he Irene... a motor boat with a 165-ton displacement. On a supporting frame of 1/4" steel rods spaced about 4" apart, Nervi spread eight layers of wire mesh, four on each side of the rods, which were tied tightly together and plastered by hand with a rich cement mortar. The resultant ferrocement was 1 3/8" thick (about the same thickness as Lambot's boat). Other than the rods sandwiched into the mesh, no formwork was needed."

"In 1947 [Nervi] built his first ferrocement structure on land, a storage warehouse... 35' x 70' and all four... walls [and] roof were of ferrocement 1 3/16" thick, their thinness made structurally feasible by their corrugated shapes."

"The following year Nervi designed and built a 41' ... the Nennele... the hull's total thickness was less than 1/2"."

"Nervi's first used of ferrocement in an important public structure was in the 1948 Exposition Hall in Turin. ...The great corrugated roof is... ferrocement panels 1 1/2" thick tied together by ribs of conventional poured concrete..."

"In the 1953 Milan Fair building and in the 1959 Flaminio stadium... Nervi used ferrocement corrugations... in strikingly cantilered roofs. A further use by Nervi of the material has been in... smooth, lightweight forms into which conventional poured concrete could be molded..."

"Most of the more recent use of ferrocement have been by others, but it is to the insight and pioneering work of that they owe their successes."

"Ferrocement is a form of reinforced concrete... [utilizing] closely spaced multiple layers of mesh or fine rods completely embedded in cement mortar. It can be formed into thin panels or sections, mostly less than 1 in. (25 mm) thick... Unlike conventional concrete, ferrocement reinforcement can be assembled into its final desired shape and the mortar... plastered directly in place without the use of a form."

"[T]he early work of Lambot... was one of the first applications of , but [was] also... a form of . His patent on wire-reinforced boats that was issued in 1847... This was the birth of reinforced concrete, but subsequent development differed from Lambot’s concept. The technology of the period could not accommodate the time and effort needed to make mesh of thousands of wires. Instead, large rods were used to make what is now called conventional reinforced concrete, and the concept of ferrocement was almost forgotten for 100 years."

"Portland cement is generally used, sometimes blended with a . The filler... is usually a well-graded sand capable of passing a 2.36 mm (No. 8) sieve. However, depending upon the... reinforcing material (mesh opening, distribution, etc.), a mortar containing some small-size gravel may be used. ...Addition of short and discrete fibers of different types favorably affects the control of cracking and the capacity... to resist tensile loads. ...[R]elatively short and slender (l/d = 100) steel fibers may be randomly distributed in hydraulic cement mortars... the overall effect being to increase tensile strength and improve the shear resistance..."

"This study aims to assess the properties of foamed concrete with a density of around 500, 700, 800 and 1000 kg/m³ formed by using a synthetic polymer-based foaming agent. The distribution of pores, wet and dry density and compressive strengths were evaluated. In addition, the creep deformations... were measured."

"Foamed concrete with higher densities (700 and 800 kg/m³) showed similar characteristics of pores, which were different from those of samples with a density of 500 kg/m³."

"equal to 5.9... 5.1... 3.8... and 1.4... MPa was obtained for foamed concrete with a density of [1000, 800, 700 and 500] kg/m3, respectively. The obtained compressive strengths were higher than those found in the literature..."

"Due to sustainable development and the related reduction in energy consumption and CO2 emission... lightweight concrete, aerated concrete and foamed concrete are increasingly used..."

"Foamed concrete (FC) is classified as lightweight concrete with a density ranging from 280 to 1800 kg/m³... and with a minimum of 20% of air pore volume in the cementitious mix..."

"Foamed concrete was made using the pre-foaming method with physical foaming or mixing and the foaming method with chemical foaming..."

"Foamed concrete is characterized by its ability to flow, self-compact and self-level as well excellent thermal and acoustic insulation..."

"The compressive strength ranges from 0.21 to 10.34 MPa for a density of 300 to 1600 kg/m³ ...[in] typical application."

"Amran et al... Fadila et al... Kang... Fernando et al... and Portal et al... produced foamed concrete for use in wall panels. Rum et al... used foamed concrete as a component in a profiled composite slab. Kadela et al.., Drusa et al.., Tian et al... and Lee at al... used foamed concrete in a pavement or floor structure to transmit a load on a subsoil, including weak soil. Moreover, foamed concrete has been used in building foundations..."

"[F]oamed concrete has the potential to become a mainstream material that uses waste material successfully as a replacement for cement or fine aggregate..."

"The components of foamed concrete (type of cement... water... water/binder ratio... additives... and admixtures...) have a significant effect on its properties..."

"Even foamed concrete with a compressive strength of 70 MPa can be made by the addition of polypropylene fiber and fine and used in high-performance cement..."

"Foamed concrete (FC) is a high-quality building material with densities from 300 to 1850 kg/m3, which can have potential use in civil engineering, both as insulation from heat and sound, and for load-bearing structures. However, due to the nature of the cement material and its high porosity, FC is very weak in withstanding tensile loads; therefore, it often cracks in a plastic state, during shrinkage while drying, and also in a solid state."

"Several factors... affect the mechanical properties of FRFC, namely: fresh and hardened densities, particle size distribution, percentage of ic material... and volume of chemical foam agent. ...rheological properties ...are influenced by the properties of both fibres and foam; therefore, it is necessary to apply an additional dosage of a foam agent to enhance the adhesion and cohesion between the foam agent and the cementitious filler in comparison with materials without fibres."

"Various types of fibres allow the reduction of... autogenous shrinkage [by] a factor of 1.2–1.8 and drying shrinkage by a factor of 1.3–1.8."

"Incorporation of fibres leads to only a slight increase in the compressive strength of foamed concrete; however, it can significantly improve the (up to 4 times), tensile strength (up to 3 times) and impact strength (up to 6 times)."

"[T]he addition of fibres leads to practically no change in the heat and sound insulation characteristics of foamed concrete..."

"FRFC... has applications in various areas of construction, both in the construction of load-bearing and enclosing structures."

"Foamed concrete (FC) has recently become widespread building material for thermal insulation and structural purposes..."

"At its core, FC is made from a concrete mixture into which pre-prepared foam is introduced, creating a system of closed voids within the hardened composite..."

"FC, which is one of the varieties of cellular concrete[,] attracts... builders worldwide... has nice workability... can be used for thermal and sound isolation, flame protection as well as blast viscosity; nevertheless, low mechanical and physical characteristics... limit the scope of its application in concrete structures."

"[A]ttributable to a large amount of entrained air, the hardening mixture is subject to shrinkage to a large extent."

"The utilization of different fibres... reduce[s] shrinkage cracks and improve[s] mechanical properties, particularly tensile and flexural..."

"FC... reduces construction expenses and allows for sustainable designs with low weight..."

"To increase the target at least up to 25 MPa [3,626 psi], engineers have applied various modern approaches... In the making of high strength [cement], low water to binder ratio (w/b) and the inclusion of , , and ultrafine silica powder are recommended as a substitute to sand..."

"To increase FC’s mechanical characteristics, the water-binding ratio w/b is usually maximally reduced, as well as the use of finely dispersed ic raw materials as a replacement for fine aggregate..."

"Incorporation of randomly oriented fibres into foamed concrete can improve load transfer in different directions, and increases due to the creation of an elastoplastic composite... in load-bearing structures..."

"Considering that fibreglass also increases mechanical strength, this is an important factor in FC’s stability... High-strength foamed concrete is obtained by introducing (PP) fibre into the raw mix... Many of the currently used fibres have been investigated, including PP... blend of polypropylene with glass... ... ... steel... palm oil, coconut... and other fibres... introduced in an amount of 0.2–1.5% volume of the concrete mixture; however, in this article, the fibre content ranges upper limit has been extended to 5%. As an alternative to traditional reinforcement, one strategy with composite mesh and mesh combined with fibre has also been studied for lightweight foamed concrete (LWFC)..."

"Using synthetic and natural fibres (glass and carbon ones) in FRFC has shown excellent durability properties with reduced drying shrinkage, high modulus of elasticity and increased mechanical strength..."

"Except for some papers... the developed FRFC has a 28-day tensile and compressive strength not even more than 2.5 MPa and 50 MPa, respectively."

"[T]he use of fibres (e.g., synthetic, metallic and natural fibres) as reinforcement is reported as an effcient material added into the fibre-reinforced FC (FRFC) matrix... to bridge the cracks... [reduce] shrinkage crack[s], to enhance load transfer and to improve the hardened properties by altering the characteristic brittle behavior [in]to elastic–plastic behavior, particularly, the flexural and tensile properties."

"The fibre matrix interface and matrix densification can deliver a greater load carrying capacity of FC reliant on the toughness of the fibres. The FRFC prolongs post-crack ductility even... [with] repeating loading cycles."

"This paper reviews the production of FC, type of foam agents, method of foaming generation, type of fibres used and factors affecting the mechanical properties of FRFC. [It also provides] a critical review on the properties and behaviors of FRFC as well as... research development trends to generate... insights into the potential applications of FRFC as suitable concrete materials... robust FRFC composites, for modern buildings and civil engineering applications... to draw a more complete picture of the current state-of-the-art."

"Axel Erikson was the first to patent -based FC technology in the year 1923... The characteristics, behaviour and structural applications of FC have been widely investigated..."

"FC is reportedly proved to be superior to conventional concrete mainly due to its lower density, which helps in reducing the static construction loads, foundation volume, labour, transportation, and exploitation expenses..."

"Many countries like the United Kingdom, Germany, Philippines, Turkey, and Thailand have made the use of FC in many construction applications..."

"The bubbles’ volume varies from 6% to 35% of the total final mixture in most of FC applications..."

"Foam agents are inorganic and organic compounds... in pellet or powder foam. Organic agents are , hydrazocarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylene tetramine, toluenesulfonyl hydrazide, benzene sulfonyl , and barium azodicarboxylate. While inorganic agents are NaHCO3, NH4HCO3, (NH4)2CO3, and Ca(N3)2... foams are used as insulation spray for air-sealing buildings. stabilizer is added to enhance its slurry viscosity which consists of 20% of 40% of and 40% of hydroxypropyl methyl cellulose... [T]he various foam agents are available in E-markets worldwide."

"The chemical foamer is ordinarily protein-based, hydrolysed protein, detergents, synthetic, , soaps of resin, and glue resins... The protein foamers form in a more grounded and enclosed cell of air-void structure, which allows the incorporation of a more prominent volume of bubble and gives a higher steady bubble network. In contrast, the synthetic ones abdicate more prominent extension and hence lower density... [T]he extreme use of chemical foam volume causes a decrease in flow, density and mechanical properties of FC... However, FC’s flow is considerably influenced by the time of mixing, showing that the lengthy mixing can result in the damage of the enclosed cell of air-voids by plummeting the air content..."

"Reportedly, FC’s mechanical properties are commonly dependent on the volume of foam content instead of its dependence over the proportion of water and cement..."

"Fibre-reinforced concrete (FRC) is one containing fibrous material that improves its structural solidity..."

"Basalt fibre is cut from a continuous basalt fibre with a diameter of 17 μm, 2.5 times superior in tensile strength to superior steel. Average fibre length: 6 to 24 mm. Recommendations for the dosage of basalt fibre: 1 kilogram per 1 cubic meter of mortar or concrete. It is necessary to introduce it into the mix with water, after stirring the fibre until it is evenly distributed in the water, it is necessary to slightly increase the mixing time (up to 5–10 min) for uniform distribution in volume."

"For fibreglass concrete, an alkali-resistant (AR) fibre should be used."

"PVA fibres have a higher tensile strength [1300 MPa] than [other] synthetic[s] and are relatively economical... Due to its low density... the fibre is ideal for foamed concrete... the is 25 GPa..."

"[P]olypropylene fibre, despite the low modulus of elasticity (1.5–10 GPa), has relatively high durability... an even lower density than PVA... [and is] ideal for foam concrete. The... tensile strength is 240–760 MPa and the ultimate elongation is 15–80%..."

"[F]ibres content should be controlled within 5% to achieve optimum concrete behaviour where excessive fibres may reduce the concrete strength."

"As claimed by Lim et al... finer... aggregate size may increase the strength of FC... As the particle size grading decreased, from passing through 2.36 mm sieve to 0.60 mm and 0.10 mm sieve, the strength has an increasing trend... With finer aggregate, the workability also increases and reduces the use of compaction that potentially bursts the bubble inside concrete paste."

"Silica fume has been found to benefit concrete properties [145], especially compressive strength and durability. It was added to FRFC and was found to have a 25% increment, at most, in compressive strength..."

"With the same quantity of addition, and specimens have higher compressive strength than silica fume... [N]ano-silica also have been investigated... The 4% nano-silica was found to have more excellent mechanical properties, durability and microstructure than plain FC and 15% silica fume... Silica fume was eFFectively enhanced the flexural, compressive and tensile strength and durability with a combination of waste marble material... [T]o enhance LWFC properties, apart from traditional materials, such as FA or SF... the recycled components like the slag of various types... or glass... have also been included in the LWFC concrete matrix... [T]he pozzolans may increase the concrete strength and its durability..."

"FC is obtained from mixing base mix (normally mortar) with preformed foam (diluted foam agent with high pressure). ...FC consists of cement as binders, sand as aggregates, water, and foams. As a consideration of economic and performance enhancements, many researchers... [introduced] additives or replacements to the FC, such as fly ash... silica fume... superplasticizer... fibres, and others. There is no specific method to determine the mixing proportions. However, Kearley... proposed the calculation of mixing the proportions by the target density method, and other researchers have practiced this."

"Fibre-reinforced foam concrete mixture is poured into molds without mechanical compaction, so it must have self-sealing ."

"For optimization various performances such as consistency, rheology and workability, segregation and bleeding should be considered... These parameters mainly depend on the water/cement ratio, supplementary cementitious materials, aggregates, s, foam agents, and the type and concentration of fibre."

"[T]he mixture’s components must be precisely calculated to improve the rheology and consistency of FRFCC, attain self-sealing behaviors, and enhance the adhesion and cohesion between the foaming agent and the cementitious filler. One of the main features influencing the rheology and texture of fresh FRFCC is the mixture’s water content. Another main factor is the fibre density... the adding of light fibre negatively influences the constancy of the mixture. Besides, the rheology of FRFC worsens with excess foam due to the higher air volume, while the incorporation of SP improved the flow rate. ...[T]he "Portland cement—silica-containing additive-complex modifiers" system can significantly reduce and create easily compacted fibre-reinforced foamed concrete mixtures."

"The introduction of fibre somewhat reduces workability. The fibres large specific surface absorbs more of the cementitious mortar around the fibres and, consequently, increases the viscosity of concrete, which contributes to a slight reduction in... spreadability. However, with proper FRFC mix... improvement in workability can be achieved by introducing the optimum fibre amount."

"The principle of the segregation and bleeding (water separation) test is that after sampling, the concrete mixture is left for 15 min... After that, the upper part of the sample is poured onto a sieve with a mesh size of 5 mm. After two minutes... [t]he stratification coefficient is calculated as the mixture ratio above the sieve to [that below it]."

"[[w:Superplasticizer|[S]uperplasticizers]], if used to reduce w/c, do not cause separation or water separation. The use of a clogging micro filler (for example, finely ground limestone or quartz sand) helps to reduce... water separation... [T]he micro filler [may create] an additional "stability framework," which increases... resistance to segregation..."

"[I]nclusion of fibres [having] more than one type or more than one size... [has been] recognized as hybrid fibres."

"[C]ompressive strength decreases exponentially when concrete’s density decreases... FC’s compressive strength commonly decreases gradually as the entrapped bubbles increased; however, its strength may be enhanced by adding fibres... [F]ibres can enhance its hardened [physical] properties (including... toughness and elasticity)..."

"[O]verall strengths were mainly influenced by the factor of combined water/cement and air/cement ratio..."

"The objective of this study is to develop structural fibered foamed concrete by the addition of polypropylene fiber, , and . Foamed concrete was obtained by replacing sand with fly ash. The properties of the foamed concrete were enhanced with polypropylene fiber and fine silica fume."

"Structural fibered foamed concrete with dissimilar densities of foamed concrete (1000, 1300, 1600, and 1900 kg/m³) [62, 81, 100, 119 lb/ft³] is essential for examining compressive, flexural and splitting tensile strengths, drying shrinkage and creep."

"Fine silica fume and polypropylene fiber considerably promoted the hardened strength... [P]olypropylene fiber significantly enhanced the tensile strength and increased the creep resistance and drying shrinkage."

"[S]tructural fibered foamed concrete can be used as a substitute lightweight concrete material for the production of structural concrete applications... today."

"The neat cement with fine sand was used in the fabrication of a lightweight FC with uniformly distributed micro- or macroscopic discrete air cells..."

"FC provides unique advantages, such as thermal and acoustic insulation and resistance to fire and termite attack, lowers cost in construction, and produces... eco-friendly structures..."

"Generally, FC is designed to achieve a low compressive strength around 1–10 MPa [150 to 1,500 psi] and can be applicable in filling voids and restoring trenches but cannot be used in the construction of any structural member... To achieve the desired strength of at least 25 MPa [3,600 psi]... different innovative solutions... are economically and environmentally admissible..."

"[S]mall water-to-binder (w/b) ratio and the inclusion of (SF), ultrafine powder of silica and (FA) as an alternative of sand is recommended in the production of high-strengths FC..."

"A number of studies produced FC with compressive strength of around 50 MPa [7,300 psi] by applying special curing condition and described the relationships among strength, density, and porosity..."

"The present paper attempts to develop structural fibered foamed concrete (SFFC) with 10–70 MPa [1,500-7,300 psi] compressive strength and 1000–1900 kg/m³ [62-119 lb/ft³] density."

"Ordinary (OPC)... was used to prepare the specimens... Dry and un-compacted SF with a SiO2 content of 91.9% was used... A residue of approximately 1.56% was obtained after sieving the residue through a 45 Am sieve. ...Class F FA was used in accordance with ASTM C 618... PP fiber with a 100 μm (dia.) and 10 mm (length) was used... A [protein-based] foam agent... with an aerated density of 80 kg/m³... after diluting... [with] water... in a ratio of 1∶40 [by volume] was used... A -based super-plasticizer was applied... The dosage of the super-plasticizer and the flow of premix paste were low... [A] cohesive state was observed in the final FC mixture, in which the cementitious particle appeared... wrapped by the foam. ...[O]nly one type of middle-east sand [ 1.72] was used... spherical and smooth-surfaced..."

"Practically, a sufficient flow range in a premixed paste is a proof of the effective production of FC. When the value of flow seen was lesser than the limit, the mixes of the developed premixed paste and foam was considered in-cohesive. The binders seemed to be covered by air bubbles, which collapsed afterwards. [W]hen the value of flow was greater than the limit, seclusion happened and foam bubbles inclined to collapse."

"[A]fter 7 days of curing, the concrete without SF attained approximately 65%–80% of [compressive] strength at 28-day[s]... the specimens encompassing SF gained approximately 80%–95%... [I]n FC without SF, the 90-day strength was approximately 75%–90% of the conforming... strength. [S]pecimens encompassing SF gained around 80%–95% of the equivalent 90-day strength. Therefore, the FC with FA can gain strength over a long period."

"[L]ightweight FC material can develop strength of equal to 60 MPa [8,700 psi] with a density of approximately 60%–70% of the traditional concrete density."

"For a specified volume of foam, the PP fiber significantly improved the hardened strength. ...This advantage was also observed in the FC specimens with SF. Nevertheless... addition of PP fiber condensed the flowability of mix. Thus, we increased dosage... 0.8% fiber content was the best... level on the basis of a swap between performance enhancement and flowability loss."

"FC is a type of cement mortar containing cement, water, and stable and homogeneous foam introduced using a suitable foaming agent... regarded as self-compacting materials..."

"Other academic terms describing this material are lightweight cellular concrete, low-density foam concrete, or cellular lightweight concrete, etc..."

"The textural surface and microstructural cells make it widely used in the fields of the thermal insulation... sound absorbance... and fire resistance..."

"A great number of environmentally friendly buildings using FC as nonstructural members have been built in recent years... It is also used for bridge filling to eliminate differential settlement... In addition, the applications for prefabricated components production... building foundation... and airport buffer system are also reported..."

"Foam concrete has been commonly used in construction applications in different countries such as Germany, USA, Brazil, UK, and Canada..."

"This material has renewed interests in terms of underground engineering. This is the requirement of underground structure to control the overlying dead load... whereas the controllable density and low self-weight... could be effectively used for reducing the dead load. Other properties, such as seismic resistance, ideal coordinated deformation capacity, and easy pumping...enhance the popularity of this material..."

"FC has been quickly promoted as construction materials for tunnels and underground works. Its excellent self-flowing capacity can be used to fill voids, sink holes, disused sewage pipes, abandoned subways, and so on. The low and controlled self-weight makes it capable for load reduction or liner elements in tunnel and metro systems..."

"Tan et al.... performed an investigation on compression deformation properties of FC used as liner element for the purpose of further explaining stress and strain response. The experimental results indicated that the of FC increases with density and confining pressure, whereas the modulus of elasticity has a positive correlation only with densities regardless of confining pressure. And no notable correlation was observed between peak strain and density, but peak strain increases with confining pressure."

"Tikalsky et al.... studied the freeze-thaw durability of cellular concrete and proposed an improved freeze-thaw test method. They reported that depth of absorption was considered as a critical predictor in developing freeze-thaw-resistant concrete, which will contribute to promote effectiveness in terms of using FC as insulation material for tunnels in cold regions."

"Sun et al... explored the influence of different foaming agents on compressive strength, drying shrinkage, and workability of FC, which will be helpful to determine specification and implementation details."

"Amran et al... reviewed the composition, preparation process, and properties of FC..."

"[T]he focus of... Ramamurthy et al... is to classify literatures on foaming materials, foaming agents, cement, fillers, mix proportion, production methods, fresh and hardened properties of FC, etc."

"The objective of this review is to highlight engineering properties, material properties, and the practical applications in tunnel and underground engineering."

"There is a confusion... between FC and similar materials in early literatures, i.e., aerated concrete and air-entrained concrete... However, one definition (i.e., FC is defined as a cementing material with the minimum of 20% foams by volume in the mixed plastic mortar) introduced by Van Dijk... clearly distinguish the FC from aerated concrete... and air-entrained concrete... The closed air-voids system in FC notably reduces its density and weight and at the same time produces efficient insulation and fire resistance capacity..."

"The first Portland cement-based FC was patented by Axel Eriksson in 1923, and then, small-scale commercial production activities were launched... Valora carried out the first comprehensive investigation in the 1950s..."

"Rudnai... and Short and Kinniburgh... [in 1963] systematically reported the composition, properties, and applications of the FC..."

"FC was initially envisaged as a void filling, stabilization, and insulation material..."

"The booming development of this new constituent material in buildings and constructions was enhanced in the late 1970s... A government-oriented assessment on FC could be seen as a milestone event to further widening FC applications."

"Over the past 30 years, FC are widely used for the bulk filling... ditch repair, retaining wall...bridge backfill... slab structure of concrete floor... and housing insulation... etc. ...Currently, people are increasingly interested in using it as a nonstructure or semistructure member for underground engineering, such as grouting works for tunnels, damage treatment, and liner structures."

"The basic components of FC consist of (1) water, (2) binder, (3) foaming agent, (4) filler, (5) additive, and (6) fiber."

"The water requirement for constituent material depends on composition, consistency and stability of the mortar body..."

"[L]ower water content leads to a hard mixture... easily resulting in bubble bursting..."

"[H]igher water content causes mixture too thin to accommodate bubbles... causing bubbles separating from the mixture..."

"The (ACI) recommends that mixed water should be fresh, clean, and drinkable..."

"Cement is the most commonly used binder. The ordinary , rapid hardening Portland cement, calcium sulphoaluminate cement, and high-alumina can be used in ranges between 25% and 100% of the binder content..."

"The determines FC density by controlling generation rate of the bubbles in cement paste. The resin-based was one of the earliest used... [S]ynthetic, protein-based, composite and synthetic s have been derived and developed... the most frequently used are synthetic and protein-based..."

"Various fillers such as , , powder, granulated blast furnace , and fly-ash ceramicite... have been widely adopted... to enrich FC mechanical performances... Addition of these fillers is helpful to improve mix proportion design, long-term strength, and reduce costs. In addition, some fine aggregates such as fine sand... recycled glass powder... and surface modified chip... are commonly used for production of high-density FC."

"Commonly used additive includes the water reducer, water-proofing additive, retarder, coagulation accelerator, etc. s are... considered to enhance compatibility... [T]hey are defined as water reducers to improve performance of fresh concrete... and there is no notable impact on concrete segregation..."

"A variety of fibers are added into FC so as to improve strength and reduce shrinkage. They are mainly ... glass and polypropylene... red ... palm oil, steel... coconut... waste paper ... [and] carbon... which usually introduced in ranges between 0.2% and 1.5% of the mixture volume."

"Foamed concrete differentiates from (a) gas or aerated concrete, where the bubbles are chemically formed through the reaction of powder with calcium hydro oxide and other alkalies released by cement hydration and (b) air entrained concrete, which has a much lower volume of entrained air... for durability."

"28 days strength and dry ... vary according to its composition, largely its air voids content, but usually... range... 1.0 to 25.00 N/mm2 and 400 to 1800 kg/m3. The plastic density... is about 150 to 200 kg/m3 higher than... dry density."

"Foamed light weight concrete... bricks, blocks or poured in-situ is used for over flat roofs... cold storage walls or... s for low-rise buildings."

"Fire rating of foamed concrete is far superior to... brick work or dense concrete."

"[D]ry ingredients like cement, sand, sand + fly ash or fly ash alone shall be... thoroughly mixed to ensure even distribution... [B]locks may be de-moulded after 24 hours"

"[F]oam... shall be added in measured amount to the slurry of cement, sand, fly ash and water in the batch mixer... mixing to get uniform consistency... of desired wet unit weight..."

"After curing [per IS: 456-2000], the blocks shall be allowed to dry under shade for a period 2 to 3 weeks... to complete their initial shrinkage..."

"Sample [first trial] mix proportions [by weight of water (W), ordinary Portland cement grade 53 (OPC 53 grade or (C) in Note below), fly ash (FA), and fine sand (FS) passing 4 mm IS sieve] ... are given in table- 1, 2 & 3. However, conclusive... proportions by actual trials may be worked out... for required workability, plastic density and compressive strength."

"If [used,] ... dosage should not be more than 0.2[% by weight of cement] bwc."

"Ignore the amount of water... in the foam in the mix design calculation."

"Determine the amount of air (kg/m3) in the mix from... the target density of the foam."

"Usually... cement content lie[s] between 300 to 500 kg/m3. ...[G]ain in strength is small above... 500 kg/m3."

"Fly ash is added... up to 100% of the [ordinary Portland cement] OPC content, to enhance workability and increase long-term strength... Because of greater surface area... [these] mixes have a greater water demand... [F]ly ash... leads to a more uniform bubble structure... which... improve[s] some... engineering properties..."

"Fly ash can be used as a total replacement for sand to produce... a dry density of up to 1400 kg/m3."

"[T]rial mixes should be done... to determine workability... plastic density... [and compressive strength.] Specimens shall be cast and tested for... compliance of required specifications."

"To minimize shrinkage... [water] ratio[s] should be kept as low as possible."

"This CPAR project was undertaken to test, demonstrate, and commercialize a new construction system... [which] employs stay-in-place forms made from fiberglass-reinforced cement boards."

"Foamed concrete is also referred to as aerated or cellular concrete. Foamed concretes are lightweight concretes [typically... with densities ranging from 320 to 1,920 kg/m3 (20 to 120 lb/ft3)] that are prepared by adding air cells... typically... from 0.1 to 1 mm (0.004 to 0.04 in.) in diameter (Aldrich and Mitchell 1976)."

"The foamed concrete used in this investigation was a 500- to 880-kg/m3 (31-to 55-lb/ft3) mixture that did not contain aggregate. Admixture materials, dispersing agents, chopped synthetic fiber, and s were added to the foamed concrete to improve the strength and toughness and produce a more uniform material. The particular type of foamed concrete prepared for this research program would be classed as a neat-cement cellular concrete modified with admixtures (Legatski 1994)."

"Foamed concrete is a desirable material... because of its durability, thermal-insulating, and fire-retarding properties. The low density of foamed concretes produces a substantial reduction in the dead weight of the structures in which it is used."

"Foamed-concrete panels are... an economical component in construction because they are not subject to attack by insects or fungi. Foamed concrete will not degrade or depolymerize because of oxidation or photolytic reactions. In the event of fire, foamed concrete will slow the spread of the fire and will not emit smoke or toxic fumes (Short and Kinniburgh 1981, 1978)."

"As the density of foamed concrete decreases, the strength properties and thermal conductivity decrease... Foamed concretes are generally used in nonstructural applications such as roof decks over metal formwork, void-filling grouts, and shock-absorbing materials for special applications."

"Foamed-concrete blocks or panels are produced as cast-in-place (or cast-onsite) or precast units. Precast blocks or panels are generally manufactured by using chemical additives to generate gas bubbles in the concrete mixture. ...[C]uring is typically done under high-pressure steam."

"Cast-onsite operations typically use rotating drum or paddle mixers. The cellular structure is produced by introducing a preformed, aqueous-based foam similar to a fire-fighting foam."

"The new method of using cast-in-place foamed concrete with stay-in-place forms... offers several advantages. ...[It] can be adapted to a variety of requirements, and the new construction system... [a]llows hollow spaces to be blocked out in the walls for the installation of utilities or for steel-reinforced concrete pilasters that are integral with the wall."

"The strength of foamed concrete made with conventional portland cement can be maximized by combining the mixture design that offers the highest paste strength with the optimum mixing techniques. Previous engineering studies (Pier and Pahl 1994) show that for a given density of foamed concrete, the strength... increases as the strength of the cured paste increases..."

"High-strength concretes designed with conventional materials typically improve the strength of the cured concrete by reducing the water/cement ratio (w/c) using a high-range water-reducing admixture (HRWRA) and by replacing up to 15 percent of the mass of cement with . ...The addition of silica fume... allows the formed by the hydration of the cement to react and form additional calcium silicate hydrate gel that increases the strength of the paste. The design strategy used in this study involved investigating a silica-fume replacement of up to 15 percent and the use of high-range water reducers that allowed samples with w/c's as low as 0.44 to be prepared."

"Pier and Pahl (1994) also found that the strongest foamed concretes were made without using any fine aggregate. The fine-aggregate particles acted as stress concentrators, and samples made with any fine aggregate were weaker than the neat-cement formulations."

"An organic fiber (nylon) was used in the mixture in quantities that are approximately 1 percent by volume of the mixture... to increase the fracture toughness of the mixture."

"The character of the foaming agent (synthetic organic or various types of hydrolyzed protein) can produce significant changes in strength (Pier and Pahl 1994). Animal protein-based foaming agents and synthetic foaming agents were both evaluated in this study."

"[I]nvestigators examined several different types of mixers and developed a technique for mixing that involved the use of a high-shear mixer to make a paste and a paddle mixer to blend foam and fiber with the paste."

"Three important variables, the proportion of silica-fume replacement, the type of HRWRA, and the w/c, were evaluated... A methocellulose thickening agent (Methocel F4M, Dow Chemical Co...) was added to each batch to reduce the rate of settling of the cement particles. The mixing operation... involved dry blending the Methocel with portland cement in a 7-to-l by volume mixture prior to adding the cement to the water in the high-shear mixer. The paste was prepared by combining the water, HRWRA, dispersing agent, cement, and silica fume in a 0.36-m3 (12-ft3) capacity high-speed shear mixer. The addition of foam adds water to the mixture, and the quantity of the water depends on the density of the foam. ...[I]t was necessary to add sufficient water to the high-shear mixer to get the cement paste to mix efficiently and to flow out of the mixer."

"[P]aste was removed from the high-shear mixer and placed in a Stone Model 1265PM paddle mixer... Litecrete R11937 foaming agent... was used... diluted 39 to 1 by volume, and the diluted solution was foamed using a Cellufoam Systems Model 620 Foam Generator... Foam was added to adjust the density to the target level, and fiber was added to the foamed concrete. The foamed concrete was then removed from the paddle mixer and placed in the form..."

"Silica-fume replacement above 20 percent presents problems with regard to water demand even when HRWRA is used. ...In two of the three attempts to place foamed concrete with a 20-percent silica-fume replacement, the foamed concrete collapsed."

"The most successful placements and highest strengths were obtained with 10-percent silica-fume replacement. The best flow characteristics and best strengths were obtained with a mixture that contained 10-percent silica-fume replacement and at w/c = 0.62."

"The HRWRA ingredient that performed best was Sikament S-10 ESL (Sika Corp...) ...a synthetic HRWRA formulated around a vinyl co-polymer. The manufacturer recommends this HRWRA for use in concretes containing silica fume or other micro-silica products. The manufacturer's recommended addition rate is 390 to 1,300 ml/100 kg of cement. Additions of... 1,200 ml/100 kg of combined cement and silica fume were used..."

"Typically, the samples from the lowest part of the column were 16 to 32 kg/m3 (1 to 2 lb/ft3) denser than the samples from the top of the column. In extreme cases, variations as high as 320 kg/m3 (20 lb/ft3) were noted. Denser samples are stronger. In these low-density concretes, a 16- to 32-kg/m3 (1- to 2-lb/ft3) density difference can increase the unconfined compressive strength by 100 kPa (14.5 psi) or more."

"The target densities for the panels were set at 480 to 560 kg/m3 (30 to 35 lb/ft3) with target unconfined compressive strengths (28 days) of over 895 kPa (130 psi)."

"A high temperature can cause the foam to collapse because it expands the gas bubbles in the concrete and lowers the surface tension in the foam. Based on the results of the temperature measurements, a synthetic foaming agent that was considered to have better tolerance at high temperatures was substituted for the animal protein-based foam that had been used... where the foamed concrete had collapsed."

"The goal was to produce materials that had an air-dried density under 640 kg/m3 (40 lb/ft3) and an unconfined compressive strength of over 690 kPa (100 psi) after curing for 28 days..."

"The composition used in the optimum mixture proportion is presented in Table 6."

"The peak interior temperatures in the panels reached approximately 30°C above ambient... The temperature changes did not produce any thermal or shrinkage cracking. The foam collapse observed stopped when the synthetic foaming agent was used. No problems with regard to flash setting or loss of workability were noted in the temperature ranges observed... [N]o special procedures (such as cooling the ingredients) or the use of low-heat cements are needed in foamed-cement panel production for the panel sizes used in this investigation when ambient temperatures are on the order of 20 to 25 °C."

"Basically there is only one method for making concrete light i.e., by the inclusion of air in concrete. This is achieved in actual practice by three different ways. (a) By replacing the usual mineral aggregate by cellular porous or light-weight aggregate. (b) By introducing gas or air bubbles in mortar. This is known as aerated concrete. (c) By omitting sand fraction from the aggregate. This is called 'no-fines' concrete."

"[S]tructural light-weight concrete is... strong enough to be used for structural purposes. Light-weight concrete can... be classified on the purpose for which it is used, such as structural light weight concrete, non-load bearing concrete and insulating concrete. The aerated concrete which was mainly used for insulating purposes is now being used for structural purposes sometimes in conjunction with steel reinforcement. The aerated concrete is more widely manufactured and used in the Scandinavian countries; whereas in U.K., France, Germany and U.S.A. owing to the production of large scale artificial industrial light-weight aggregate, light-weight aggregates concrete is widely used."

"There are several ways in which aerated concrete can be manufactured. (a) By the formation of gas by chemical reaction within the mass during liquid or plastic state. (b) By mixing preformed stable foam with the slurry. (c) By using finely powdered metal (usually powder) with the slurry and made to react with the liberated during the hydration process, to give out large quantity of gas. This hydrogen gas when contained in the slurry mix, gives the cellular structure. Powdered may also be added in place of aluminum powder. and bleaching powder have also been used instead of metal powder. But this practice is not widely followed at present."

"Gasification method is of the most widely adopted methods using aluminium powder or such other similar material. This method is adopted in the large scale manufacture of aerated concrete in the factory wherein the whole process is mechanised and the product is subjected to high pressure steam curing i.e... the products are autoclaved. Such products will suffer neither retrogression of strength nor dimensional instability."

"The practice of using preformed foam with slurry is limited to small scale production and in situ work where small change in the dimensional stability can be tolerated. But... any density desired... can be made in this method."

"[T]he addition of a moderate amount of air to any concrete mix will bring a marked increase in resistance to the disintegrating effects of freezing and thawing."

"The application of air-entrainment to the concrete mix, for the improvement of its durability, workability and uniformity, is one of the most important developments in concrete technology."

"The improvement in durability with the use of proper amounts of entrained air in concrete is so great that variations in the , within the usual working range, do not have the same significance as formerly."

"The deliberate addition of air to concrete seemed, from a superficial examination, to be contradictory to the principle that high density is a pre-requisite of high quality. But the concept of density of concrete actually means: freedom from honeycombing and large voids resulting from inadequate consolidation or from segre­gation. Air entrainment, by enabling some reduction in water-cement ratio, tends to improve the quality of the concrete paste, and by improving workability tends to reduce segregation and improves con­solidation of the concrete."

"First experiments proved that, to obtain desirable properties of air-entrained concretes, entrained air must be approximately three percent above that which is normally present in the concrete, this brings the total amount of air to between four and five percent..."

"There are various air entraining admixtures for concrete that can be either interground with the cement during the manufacturing process or added separately at the mixer. Many of them are essentially saponifying agents, they react with the alkaline constituents of the cement to form soap and from the soap, form minute air bubbles."

"[A]ir-entrainment adds to the fluidity or slump of concrete and it is possible to restore the initial degree of stiffness by adding solids or subtracting water. Air cannot be added to a mixture without introducing unbalances in consistency and yield of the plastic concrete. ...[T]he strength of the hardened concrete depends on the consistency of the plastic concrete. Experiments have shown that for the same workability, less water is required than for ordinary concrete."

"The chief ways of producing aerated or gas concrete are by mixing air entraining agents with cement or cement and sand in special high speed or whisking mixers, by adding a given quantity of pre-formed foam to a cement or a cement sand mortar in an ordinary mixer and by adding aluminum or powder to a cement mortar."

"Aerated concrete has a very high drying shrinkage but this can be reduced by high pressure steam curing in which case or natural can with advantage be introduced to the mix."

"Owing to its high drying shrinkage... [lightweight concretes] use for cast in situ should be restricted to cases where shrinkage cracks are not of much importance."

"Lightweight concrete is normally accepted as that having a density range between 25 and 110 lb per cu ft, but even lower densities can be used when it is required solely for insulating purposes."

"Lightweight concrete can be produced in three ways: 1. By omitting the fine aggregate. This is called a 'no-fines' concrete. 2. By using lightweight aggragate. 3. By using lightweight aggregate and producing what is generall known variously as 'aerated concrete', 'cellular concrete', 'gas concrete', 'porous concrete', and 'foamed concrete'. This should not be confused with air entrained concrete which has a weight nearly equal to that of ordinary concrete and in which the proportion of air is limited to about 9 per cent."

"Aerated, cellular or gas concrete can be made in weights ranging from about 25 lb per cu ft or even less, to 110 lb per cu ft. Its most useful range is perhaps between 40 and 60 lb per cu ft. It can produced in the following ways: 1. By mixing air entraining agents with cement or cement and sand in special high speed or whisking mixers. If an ordinary mixer is used it is doubtful if sufficient air would be entrained to obtain a density as low as 90 lb per cu ft. The Cheecol process belongs to this class. 2. By making foam and and adding a given quantity of this to a cement or cement and sand mortar in the mixer. An ordinary mixer is suitable for this method. The Pyrene process belongs to this class. 3. By adding hydrogen peroxide (H2O2) to the concrete. 4. By the use of calcium carbide (Ca2C2). 5. By adding aluminum powder or powder to a cement mortar."

"Very careful mixing of the mortar with the air entraining or other agent is essential in all cases if a uniform result is to be obtained."

"If the lightest concretes (25 lb per cu ft and under) are required a neat cement mortar is used, but for heavier weights (40 lb per cu ft and above) sand, preferably very fine, may be added up to a cement/sand ratio... of 1 to 4. A higher strength/weight ratio can be obtained if cement only is used, but the addition of sand cheapens the product."

"The Use of Air Entraining Agents... The normal density produced from this system ranges from 60 to 100 lb per cu ft and the proportion of air entraining agent may be about 0.25 per cent of the mix. The quantity of air entraining agent, the cement/sand ratio, the speed of the mixer and the time of mixing are the chief factors..."

"The Use of Preformed Foam... [A]lmost any desired density of concrete can be produced... dependent almost entirely on the amount of foam added. About two per cent by volume of a foaming agent is added to the water and mixed with compressed air in a mixing tube. ...The foam is delivered ... direct into the mixer in which the cement or cement sand mortar has previously been prepared. The product can be cast in situ or used for making precast blocks."

"The effects of the incorporation of each of nine different air-entraining admixtures in concrete were investigated by the making of a large number of batches of concrete under carefully controlled laboratory conditions. The results of tests on the plastic and hardened concrete specimens from batches made in parallel with and without each admixture are presented and discussed."

"Different air entraining agents produce different amounts of air entrainment, depending upon the elasticity of the film of the bubble produced, and the extent to which the surface tension is reduced. Similarly, different quantities of air entraining agents will result in different amounts of air entrainment."

"Water/cement ratio is one of the important factors affecting the quantity of air. At very low water/cement ratio, water films on the cement will be insufficient to produce adequate foaming action. At intermediate water/cement ratio (viz. 0.4 to 0.6) abundant air bubbles will be produced. But at a higher water/cement ratio although to start with, a large amount of air entrainment is produced, a large proportion of the bubbles will be lost progressively with time."

"The grading of aggregate has shown good influence on the quantity of air entrainment. It was established that the quantity of air increased from the lowest of sand to a peak at about F.M. of 2.5, and, thereafter, decreased sharply. The sand fraction of 300 and 150 microns showed a significant effect on the quantity of air entrainment. The higher quantity of these fractions resulted in more air entrainment."

"The amount of air entrainment is found to increase with the mixing time up to a certain time and thereafter with prolonged mixing the air entrainment gets reduced."

"The temperature of concrete at the time of mixing was found to have a significant effect on the amount of air entrainment. The amount of air entrainment decreases as the temperature of concrete increases."

"The constituents of the cement especially the alkali content plays an important part in the entrainment of air in concrete. Similarly, the fineness of cement is also a factor."

"Air content is... reduced by the process of compaction, on account of the movement of air bubbles to the surface... [A]s much as 50 per cent of the entrained air may be lost after vibration for 2 1/2 minutes and as much as 80 per cent may be lost by vibration for 9 minutes."

"[A]dmixtures used in conjunction with air entraining agents will... significantly affect the amount of air entrained. The use of in concrete will reduce the amount of air entrained. Similarly, the use of calcium chloride also has the tendency to reduce and limit air entrainment."

"I interrupted the old man in midsentence and stood straight up from the rocker. It felt as if a pulse of energy ran up my spine, compressing my lungs, electrifying my skin, bringing the hairs on the back of my neck to full alert. I moved closer to the fireplace, unable to absorb its heat. "Are you saying what I think you're saying?" My brain was taking on too much knowledge. There was overflow and I needed to shake off the excess. The old man looked at nothing and said, "We are God's debris.""

"Gwell eo beroù war an oaled / Eget e ti marc'h rous ar pried (Better skewers on the fireplace than in the spouse's russet horse shed.)"

"In another moment Alice was through the glass, and had jumped lightly down into the Looking-glass room. The very first thing she did was to look whether there was a fire in the fireplace, and she was quite pleased to find that there was a real one, blazing away as brightly as the one she had left behind. "So I shall be as warm here as I was in the old room," thought Alice: "warmer, in fact, because there'll be no one here to scold me away from the fire. Oh, what fun it'll be, when they see me through the glass in here, and can't get at me!""

"In the winter on a Sunday afternoon, I can spend six hours in front of the fireplace, just looking at the flames and thinking. In the evening, I’m drunk with beautiful thoughts. My wife says to me, ‘What are you looking at?’ I say, ‘The fire.’ We have to take a step backward."

"There is nothing of greater interest connected with the Durham furnace than the manufacture of iron stove plates and their artistic embellishments. ...[T]he manufacture of iron stoves, for heating of buildings, was begun at the furnace about 1741, when controlled by George Taylor, James Logan and James Morgan, father of General , iron master. These were called the "Adam and Eve" stoves from the figures, cast on them. ...In 1745, the furnace began casting the famous "Franklin Stove," or fire-place, and continued until it blew out, 1793. They were favorably received and with minor improvements, extensively manufactured. It was the first stove made that could be utilized for baking and cooking, having an extra door above the fuel door, a plate the whole length of the stove and a descending flue the same as the Prince Rupert stove, 1678, cast in England. It was improved, 1754, by a door on one side. This was known as the Philadelphia pattern, though smaller in size. The Franklin sold at £4. 6s, each at the furnace, and at Philadelphia £18 per ton, the price varying with the metal. About 1775, a stove pattern, artistically decorated with a bony skeleton inscribed on the center of the side plates, grasping a bone in one hand in the act of striking a man, near the end of the plate, while another figure on rear end of plate is standing in a frightened attitude looking on the unequal battle. Beneath the figures is the following inscription:HIR. FEIT. MIT. MIR. DER. BITER. TOTER. BRINCT. MICH.INTOTS. NO.A free translation of this Swedish-German is "Here (man) presumes to fight with me, bitter death, but he cannot overcome death.""

""Do not repine, my friends," said Mr. Pecksniff, tenderly. "Do not weep for me. It is chronic." And with these words, after making a futile attempt to pull off his shoes, he fell into the fireplace."

"Announced by all the trumpets of the sky, Arrives the snow, and, driving o'er the fields, Seems nowhere to alight: the whited air Hides hills and woods, the river, and the heaven, And veils the farmhouse at the garden's end. The sled and traveller stopped, the courier's feet Delayed, all friends shut out, the housemates sit Around the radiant fireplace, enclosed In a tumultuous privacy of storm."

"Here's a list of Dutch paintings intended for the Salon: - Israëls, ...https://philamuseum.org/collection/object/102868 Old Friends (Silent Conversation) an old man sits in a hut by the fireplace in which a small piece of peat barely glows in the twilight. For it's a dark hut... His dog, who's grown old with him, sits beside him–those two old creatures look at each other, they look each other in the eye, the dog and the old man. ...Nothing else – the twilight, the quiet, the loneliness of those two old creatures, man and dog... that old man thinking... that face – a melancholy, satisfied, submissive expression.. .I definitely know of no other painting than this Israëls that can stand up to Millet's 'Death and the Woodcutter'... on the other hand I know of no other painting that could stand up to this Israëls than Millet's Death and the woodcutter... Moreover, I feel in my mind an irresistible desire to bring together that painting by Israëls and that other by Millet and make them complement each other.."

"It happened because one day I was sitting one side of the fireplace, and my wife was sitting on the other, and I suddenly said to her, "Wouldn’t it be a good idea to write a story about some boys on an island, showing how they would really behave, being boys and not little saints as they usually are in children’s books.” And she said, "That’s a first-class idea! You write it!" So I went ahead and wrote it."

"Lele liilii ka lehu o kapuahi (He is scattering the ashes of the fireplace)."

"The prisoner was no longer fastened to the bed save by one leg. Before the seven men had had time to recover themselves and spring upon him, he had bent over to the fireplace, reached his hand towards the furnace, then rose up, and now Thenardier, the Thenardiess, and the bandits, thrown by the shock into the back part of the room, beheld him with stupefaction, holding above his head the glowing chisel, from which fell an ominous light, almost free and in a formidable attitude."

"The grate had been removed from the wide overwhelming fireplace, to make way for a fire of wood, in the midst of which was an enormous log glowing and blazing, and sending forth a vast volume of light and heat; this I understood was the Yule-log, which the Squire was particular in having brought in and illumined on a Christmas eve, according to ancient custom."

"Our society, it turns out, can use modern art. A restaurant, today, will order a mural by Míro in as easy and matter-of-fact a spirit as, twenty-five years ago, it would have ordered one by Maxfield Parrish. The president of a paint factory goes home, sits down by his fireplace — it looks like a chromium aquarium set into the wall by a wall-safe company that has branched out into interior decorating, but there is a log burning in it, he calls it a fireplace, let’s call it a fireplace too — the president sits down, folds his hands on his stomach, and stares at two paintings by Jackson Pollock that he has hung on the wall opposite him. He feels at home with them; in fact, as he looks at them he not only feels at home, he feels as if he were back at the paint factory."

"A good night for the fireplace to be crackling with flames - or so he figured, Crumpling the papers he could only see As testimonials to long plateaus of emptiness."

"A woman who taught at Berkeley dropped in on me once and saw a book burning in the fireplace. She pointed at it in terror, and I explained that it was a crummy ghostwritten life of a movie star and that it was an act of sanitation to burn it rather than sending it out into the world which was already clogged with too many copies of it. But she said, "You shouldn’t burn books" and began to cry."

"And I live with the dead – my mother, my sister, my grandfather, my father... .Every day is the same – my friends have stopped coming – their laughter disturbs me, tortures me.. ..my daily walk round the old castle becomes shorter and shorter, it tires me more and more to take walks. The fire in the fireplace is my only friend – the time I spend sitting in front of the fireplace gets longer and longer.. ..at its worst I lean my head against the fireplace overwhelmed by the sudden urge – Kill yourself and then it’s all over. Why live? I light the candle – my huge shadow springs across half the wall, clear up to the ceiling and in the mirror over the fireplace I see the face of my own ghost."

"All these people come to see the White House and they see practically nothing that dates back before 1948. Every boy who comes here should see things that develop his sense of history. For the girls, the house should look beautiful and lived-in. They should see what a fire in the fireplace and pretty flowers can do for a house; the White House rooms should give them a sense of all that. Everything in the White House must have a reason for being there. It would be sacrilege merely to "redecorate" it—a word I hate. It must be restored—and that has nothing to do with decoration. That is a question of scholarship."

"There is one great thing that you men will all be able to say after this war is over and you are home once again. You may be thankful that twenty years from now when you are sitting by the fireplace with your grandson on your knee and he asks you what you did in the great World War II, you won't have to cough, shift him to the other knee and say, "Well, your Granddaddy shoveled shit in Louisiana." No, Sir, you can look him straight in the eye and say, "Son, your Granddaddy rode with the Great Third Army and a Son-of-a-Goddamned-Bitch named Georgie Patton!"

"In small rooms... the chimney often smokes unless the door or window be open, not only because the fire devours and carries off a large quantity of the air of the room, but also because the fire requires a continual supply of air for its support; so that, if a proportional quantity of air which the fire consumes and sends up the chimney does not enter the room (which it cannot do in small rooms with a large fire), the fire languishes, and the smoke increases, since flame is nothing more than a kindled smoke, and smoke is only an extinguished flame, or, at least, not yet kindled."

"I don't approve of open fires. You can't think, or talk or even make love in front of a fireplace. All you can do is stare at it."

"Take a look at the simplest of objects. Let's take, for example, an old chair. It seems like nothing. But think of the universe comprised within it: the sweaty hands cutting the wood that used to be a robust tree, full of energy, in the middle of a luxuriant forest by some high mountains. The loving work that built it, the joyful anticipation of the one who bought it, the tired bodies it has helped, the pains and the joys it must have endured, whether in fancy halls or in a humble dining room in your neighbourhood. Everything, everything shares life and has its importance! Even the most worn down of chair carries inside the initial force of the sap climbing from the earth, out there in the forest, and will still be useful the day when, broken into kindling, it burns in some fireplace."

"Lyndon's gone and dragged Nasser away from the fireplace and onto the balcony again. Once you get him out there, it's a helluva job to get him back to the fireplace again."

"Till more effectual methods can take place, it would be of great service, to oblige all those Trades who make use of large Fires, to carry their Chimnies much higher into the air than they are at present..."

"Workmen should be consulted, and encouraged to make experiments, whether a particular construction of the Chimnies would not assist in conveying off the Smoke, and in fending it higher into the air before it is dispersed."

"[N]ear half the children that are born and bred in London die under two years of age. ...[T]he constant and unremitting Poison is communicated by the foul Air, which, as the Town still grows larger, has made regular and steady advances in its fatal influence. ...[W]e are accustomed to read with great composure of the deaths of thosands of infants, suffocated every Year by Smoke and Stenches which good policy might in a great measure remove."

"And what is all this, but that Hellish and dismall Cloud of SEA-COALE? which is not onely perpetually imminent over her head... so universally mixed with the otherwise wholsome and excellent Aer, that her Inhabitants breathe nothing but an impure and thick Mist, accompanied with a fuliginous and filthy vapour, which renders them obnoxious to a thousand inconveniences, corrupting the Lungs, and disordering the entire habit of their Bodies; so that Catharrs, Phthisicks, Coughs and Consumptions, rage more in this one City, than in the whole Earth besides."

"[N]ot from the Culinary fires, which for being weak, and lesse often fed below, is with such ease dispelled and scattered above, as it is hardly at all discernible, but from some few particular Tunnells and Issues, belonging only to Brewers, Diers, Lime-burners, Salt, and Sope-boylers, and some other private Trades, One of whose Spiracles alone, does manifestly infest the Aer, more than all the Chimnies of London put together besides."

"Whilst these are belching it forth their sooty jaws, the City of London resembles the face rather of Mount Ætna, the Court of Vulcan, , or the Suburbs of Hell, than an Assembly of Rational Creatures... For when in all other places the Aer is most Serene and Pure, it is here Ecclipsed with such a Cloud of Sulphure, as the Sun itself... is hardly able to penetrate... and the weary Traveller, at many Miles distance, sooner smells, than sees the City to which he repairs."

"It seems that those who have hitherto built or caused chimneys to be erected, have only taken care to contrive in the chambers certain places where wood may be burnt, without making a due reflection that the wood in burning ought to warm those chambers, and the persons who are in them; at least, it is certain that but a very little heat is felt of the fire made in the ordinary chimneys, and that they might be ordered so as to send forth a great deal more, only by changing the disposition of their jambs and wings."

"A plate of iron or copper bowed or bended after such a manner as is not at all disagreeable to the sight; a void behind, divided by certain small iron bands or partition plates, forming several spaces that have a communication one with another; a little vent hole in the middle of the hearth, a register plate in the upper part of the funnel; and for some shafts, a capital on the top, make up the whole construction and workmanship of our modern chimney. Now, can there be anything more simple or plain, or more easy to execute?"

"To be able to kindle a fire speedily, and make it, if you please, flame continually, whatever wood is burning, without the use of bellows; to give heat to a spacious room, and even to another adjoining, with a little fire; to warm one's self at the same time on all sides, be the weather ever so cold, without scorching; to breathe a pure air always fresh, and to such a degree of warmth as is thought fit; to be never annoyed with smoke in one's apartment, nor have any moisture therein; to quench by one's self, and in an instant, any fire that may catch in the tunnel of a chimney; all these are but a few of the effects and properties of these wonderful machines, not withstanding their apparent simplicity. Since I used this sort of chimney, I have not been troubled one moment with smoke, in a lodging which it rendered before untenable as soon as a fire was lighted; I have always inhaled, even during the sharpest seasons, a fresh air like that of the spring. In 1709, water that froze hard everywhere else very near the hearth, did not congeal at night in my chamber, though the fire was put out before midnight; and all that was brought thither in the day soon thawed; neither did I ever perceive the least moisture in winter, not even during thaws."

"In an edition of the author's writings on electrical and philosophical subjects, published in London in the year 1769, the following note is appended to this tract. "Soon after the foregoing piece was published, some persons in England, in imitation of Mr. Franklin's invention, made what they call Pennsylvanian Fire-places, with improvements; the principal of which pretended improvements is, a contraction of the passages in the air-box, originally designed for admitting a quantity of fresh air, and warming it as it entered the room. The contracting [of] these passages gains indeed more room for the grate, but in a great measure defeats their intention. For, if the passages in the air-box do not greatly exceed in dimensions the amount of all the crevices by which cold air can enter the room, they will not considerably prevent, as they were intended, the entry of cold air through the crevices.""

"[A]ny new proposal for saving the wood, and for lessening the charge and augmenting the benefit of fire, by some particular method of making and managing it, may at least be thought worth consideration."

"1. Air is rarefied by heat, and condensed by cold, that is, the same quantity of air takes up more space when warm than when cold. This may be shown... Take any clear glass bottle (a stript of the straw is best), place it before the fire, and, as the air within is warmed and rarefied, part of it will be driven out of the bottle; turn it up, place its mouth in a vessel of water, and remove it from the fire; then, as the air within cools and contracts, you will see the water rise in the neck of the bottle, supplying the place of just so much air as was driven out. Hold a large hot coal near the side of the bottle, and, as the air within feels the heat, it will again distend and force out the water. Or, fill a bladder not quite full of air, tie the neck tight, and lay it before a fire as near as may be without scorching the bladder; as the air within heats, you will perceive it to swell and fill the bladder, till it becomes tight, as if full blown; remove it to a cool place, and you will see it fall gradually, till it becomes as lank as at first."

"2. Air rarefied and distended by heat is specifically lighter than it was before, and will rise in other air of greater density. As wood, oil, or any other matter specifically lighter than water, if placed at the bottom of a vessel of water will rise till it comes to the top; so rarefied air will rise in common air, till it either comes to air of equal weight, or is by cold reduced to its former density."

"[I]n any chimney, the air over the fire is rarefied by the heat, becomes lighter, and therefore immediately rises in the funnel, and goes out; the other air in the room (flowing towards the chimney) supplies its place, is rarefied in its turn, and rises likewise; the place of the air thus carried out of the room, is supplied by fresh air coming in through doors and windows, or, if they be shut, through every crevice with violence, as may be seen by holding a candle to a key-hole."

"If the room be so tight as that all the crevices together will not supply so much air as is continually carried off, then, in a little time, the current up the funnel must flag, and the smoke, being no longer driven up, must come into the room."

"1. Fire... throws out light, heat, and smoke (or fume.) The [first] two... move in right lines, and with great swiftness; the latter is but just separated from the fuel, and then moves only as it is carried by the stream of rarefied air; and without a continual accession and recession of air, to carry off the smoky fumes, they would remain crowded about the fire, and stifle it."

"2. Heat may be separated from the smoke as well as from the light, by means of a plate of iron, which will suffer heat to pass through it without the others."

"3. Fire sends out its rays of heat, as well as rays of light, equally every way; but the greatest sensible heat is over the fire, where there is, besides the rays of heat shot upwards, a continual rising stream of hot air, heated by the rays shot round on every side."

"[C]onsider the fire-places heretofore in use, viz. 1. The large open fire-places used in the days of our fathers, and still generally in the country, and in kitchens. 2. The newer-fashioned fire-places, with low breasts and narrow hearths. 3. Fire-places with hollow backs, hearths and jambs of iron, (described by M. Gauger, in his tract entitled La Méchanique de Feu,) for warming the air as it comes into the room. 4. The Holland stoves, with iron doors opening into the room. 5. The German stoves, which have no opening in the room where they are used, but the fire is put in from some other room, or from without. 6. Iron pots, with open charcoal fires, placed in the middle of a room."

"1. The first of these methods has generally the conveniency of two warm seats, one in each corner; but they are sometimes too hot to abide in, and, at other times, incommoded with the smoke; there is likewise good room for the cook to move, to hang on pots, &c. Their inconveniences are, that they almost always smoke, if the door be not left open; that they require a large funnel, and a large funnel carries off a great quantity of air, which occasions what is called a strong draft to the chimney, without which strong draft the smoke would come out of some part or other of so large an opening, so that the door can seldom be shut; and the cold air so nips the backs and heels of those that sit before the fire, that they have no comfort till either screens or settles are provided (at a considerable expense) to keep it off, which both cumber the room, and darken the fire-side. A moderate quantity of wood on the fire, in so large a hearth, seems but little; and, in so strong and cold a draft, warms but little; so that people are continually laying on more. In short, it is next to impossible to warm a room with such a fire place; and I suppose our ancestors never thought of warming rooms to sit in; all they purposed was, to have a place to make a fire in, by which they might warm themselves when cold."

"2. Most of these old-fashioned chimneys in towns and cities have been, of late years, reduced to the second sort mentioned, by building jambs within them, narrowing the hearth, and making a low arch or breast. It is strange, methinks, that though chimneys have been so long in use, their construction should be so little understood till lately, that no workman pretended to make one which should always carry off all smoke, but a chimney-cloth was looked upon as essential to a chimney. This improvement, however, by small openings and low breasts, has been made in our days; and success in the first experiments has brought it into general use in cities, so that almost all new chimneys are now made of that sort, and much fewer bricks will make a stack of chimneys now than formerly. An improvement so lately made may give us room to believe, that still farther improvements may be found to remedy the inconveniences yet remaining. For these new chimneys, though they keep rooms generally free from smoke, and, the opening being contracted, will allow the [house] door to be shut, yet, the funnel still requiring a considerable quantity of air, it rushes in at every crevice so strongly, as to make a continual whistling or howling; and it is very uncomfortable, as well as dangerous, to sit against any such crevice. Many colds are caught from this cause only, it being safer to sit in the open street; for then the pores do all close together, and the air does not strike so sharply against any particular part of the body."

"[M]any of the diseases proceeding from colds, as fevers, pleurisies, &c., fatal to very great numbers of people, may be ascribed to strong-drawing chimneys, whereby, in severe weather, a man is scorched before, while he is froze behind."

"In the mean time, very little is done by these chimneys towards warming the room; for the air round the fire-place, which is warmed by the direct rays from the fire, does not continue in the room, but is continually crowded and gathered into the chimney by the current of cold air coming behind it, and so is presently carried off."

"In both these sorts of fire-places, the greatest part of the heat from the fire is lost; for, as fire naturally darts heat every way, the back, the two jambs, and the hearth drink up almost all that is given them, very little being reflected from bodies so dark, porous, and unpolished; and the upright heat, which is by far the greatest, flies directly up the chimney. Thus five sixths at least of the heat (and consequently of the fuel) is wasted, and contributes nothing towards warming the room."

"3. To remedy this, the Sieur Gauger gives, in his book, entitled La Méchanique de Feu, published in 1709, seven different constructions of the third sort of chimneys mentioned above, in which there are hollow cavities made by iron plates in the back, jambs, and hearths, through which plates the heat passing warms the air in those cavities, which is continually coming into the room fresh and warm. The invention was very ingenious, and had many conveniences; the room was warmed in all parts, by the air flowing into it through the heated cavities; cold air was prevented rushing through the crevices, the funnel being sufficiently supplied by those cavities; much less fuel would serve, &c. But the first expense, which was very great, the intricacy of the design, and the difficulty of the execution, especially in old chimneys, discouraged the propagation of the invention; so that there are, I suppose, very few such chimneys now in use. The upright heat, too, was almost all lost in these, as in the common chimneys."

"4. The Holland iron stove, which has a flue proceeding from the top, and a small iron door opening into the room, comes next to be considered. Its conveniences are, that it makes a room all over warm; for, the chimney being wholly closed except the flue of the stove, very little air is required to supply that, and therefore not much rushes in at crevices, or at the door when it is opened. Little fuel serves, the heat being almost all saved; for it rays out almost equally from the four sides, the bottom, and the top, into the room , and presently warms the air around it, which, being rarefied, rises to the ceiling, and its place is supplied by the lower air of the room, which flows gradually towards the stove, and is there warmed, and rises in its turn, so that there is a continual circulation till all the air in the room is warmed. The air, too, is gradually changed, by the stove-door's being in the room, through which part of it is continually passing, and that makes these stoves wholesomer, or at least pleasanter than the German stoves... But... There is no sight of the fire... When the room is warm, people, not seeing the fire, are apt to forget supplying it with fuel... The change of air is not carried on quite quick enough; so that, if any smoke or ill smell happens in the room, it is a long time before it is discharged. For these reasons the Holland stove has not obtained much among the English (who love the sight of the fire) unless in some workshops..."

"5. The German stove is like a box, one side wanting. It is composed of five iron plates, screwed together, and fixed so as that you may put the fuel into it from another room, or from the outside of the house. It is a kind of oven reversed, its mouth being without, and body within, the room that is to be warmed by it. This invention certainly warms a room very speedily and thoroughly with little fuel; no quantity of cold air comes in at any crevice, because there is no discharge of air which it might supply, there being no passage into the stove from the room. ...Its inconveniences are, that people have not even so much sight or use of the fire as in the Holland stoves, and are, moreover, obliged to breathe the same unchanged air continually, mixed with the breath and perspiration from one another's bodies, which is very disagreeable to those who have not been accustomed to it."

"6. Charcoal fires in pots are used chiefly in the shops of handicraftsmen. They warm a room (that is kept close, and has no chimney to carry off the warmed air,) very speedily and uniformly; but, there being no draft to change the air, the sulphurous fumes from the coals (be they ever so well kindled before they are brought in, there will be some,) mix with it, render it disagreeable, hurtful to some constitutions, and some times, when the door is long kept shut, produce fatal consequences."

"To avoid the several inconveniences, and at the same time retain all the advantages of other fire-places, was contrived the PENNSYLVANIAN FIRE-PLACE, now to be described."

"[T]he flame and smoke will ascend and strike the top... which will thereby receive a considerable heat. The smoke, finding no passage upwards, turns over the top of the air-box, and descends between it and the back plate to the holes in the bottom plate, heating, as it passes, both plates of the air-box, and the said back plate; the front plate, bottom and side plates are also all heated at the same time. The smoke proceeds in the passage that leads it under and behind the false back, and so rises into the chimney."

"The air of the room, warmed behind the back plate, and by the sides, front, and top plates, becoming specifically lighter than the other air in the room, is obliged to rise; but the closure over the fire place hindering it from going up the chimney, it is forced out into the room, rises by the mantel-piece to the ceiling, and spreads all over the top of the room, whence being crowded down gradually by the stream of newly-warmed air that follows and rises above it, the whole room becomes in a short time equally warmed."

"At the same time, the air, warmed under the bottom plate and in the air-box, rises and comes out of the holes in the side plates, very swiftly, if the door of the room be shut, and joins its current with the stream before mentioned, rising from the side, back, and top plates."

"The air that enters the room through the air-box is fresh, though warm; and, computing the swiftness of its motion with the areas of the holes, it is found that near ten barrels of fresh air are hourly introduced by the air-box; and by this means the air in the room is continually changed, and kept at the same time sweet and warm."

"It is to be observed, that the entering air will not be warm at first lighting the fire, but heats gradually as the fire increases."

"Its advantages above the common fire-places are, 1. That your whole room is equally warmed, so that people need not crowd so close round the fire, but may sit near the window, and have the benefit of the light for reading, writing, needlework, &c. They may sit with comfort in any part of the room... 2. If you sit near the fire, you have not that cold draft of uncomfortable air nipping your back and heels, as when before common fires, by which many catch cold, being scorched before, and... froze behind. 3. If you sit against a crevice, there is not that sharp draft of cold air playing on you, as in rooms where there are fires in the common way; by which many catch cold, whence proceed coughs, catarrhs, tooth-aches, fevers, pleurisies, and many other diseases. 4. In case of sickness, they make most excellent nursing-rooms; as they constantly supply a sufficiency of fresh air, so warmed at the same time as to be no way inconvenient or dangerous. A small one does well in a chamber; and, the chimneys being fitted for it, it may be removed from one room to another, as occasion requires, and fixed in half an hour. The equal temper, too, and warmth of the air of the room, is thought to be particularly advantageous in some distempers... 5. In common chimneys, the strongest heat from the fire, which is upwards, goes directly up the chimney, and is lost; and there is such a strong draft into the chimney, that not only the upright heat, but also the back, sides, and downward heats are carried up the chimney by that draft of air; and the warmth given before the fire, by the rays that strike out towards the room, is continually driven back, crowded into the chimney, and carried up by the same draft of air. But here the upright heat strikes and heats the top plate, which warms the air above it, and that comes into the room. The heat likewise, which the fire communicates to the sides, back, bottom, and air-box, is all brought into the room; for you will find a constant current of warm air coming out of the chimney corner into the room. Hold a candle just under the mantel-piece, or breast of your chimney, and you will see the flame bent outwards; by laying a piece of smoking paper on the hearth, on either side, you may see how the current of air moves, and where it tends, for it will turn and carry the smoke with it. 6. Thus, as very little of the heat is lost, when this fire-place is used, much less wood will serve you, which is a considerable advantage where wood is dear. 7. When you burn candles near this fire-place, you will find that the flame burns quite upright, and does not blare and run the tallow down, by drawing towards the chimney, as against common fires. 8. This fire-place cures most smoky chimneys, and thereby preserves both the eyes and furniture. 9. It prevents the fouling of chimneys; much of the lint and dust that contributes to foul a chimney being, by the low arch, obliged to pass through the flame, where it is consumed. Then, less wood being burnt, there is less smoke made. Again, the shutter, or trap-bellows, soon blowing the wood into a flame, the same wood does not yield so much smoke as if burnt in a common chimney; for, as soon as flame begins, smoke in proportion ceases. 10. And, if a chimney should be foul, it is much less likely to take fire. If it should take fire, it is easily stifled and extinguished. 11. A fire may be very speedily made in this fire-place by the help of the shutter, or trap-bellows... 12. A fire may be soon extinguished by closing it with the shutter before, and turning the register behind, which will stifle it, and the brands will remain ready to rekindle. 13. The room being once warm, the warmth may be retained in it all night. 14. And lastly, the fire is so secured at night, that not one spark can fly out into the room to do damage."

"With all these conveniences, you do not lose the pleasing sight nor use of the fire, as in the Dutch stoves, but may boil the tea-kettle, warm the flat irons, heat heaters, keep warm a dish of victuals by setting it on the top, &c."

"We leave it to the political arithmetician to compute how much money will be saved to a country, by its spending two thirds less of fuel; how much labor saved in cutting and carriage of it; how much more land may be cleared by cultivation; how great the profit by the additional quantity of work done, in those trades particularly that do not exercise the body so much, but that the workfolks are obliged to run frequently to the fire to warm themselves; and to physicians to say, how much healthier thick-built towns and cities will be, now half suffocated with sulphury smoke, when so much less of that smoke shall be made, and the air breathed by the inhabitants be consequently so much purer."

"[T]he builder of chimneys has been left to grope his way in the dark without assistant; and in almost every instance his attempts to improve upon the practice of his predecessors, have been unsuccessful; so that the inhabitants of these countries, with justice, complain that the inconveniencies felt in new houses from this cause, usually are more than sufficient to counterbalance all the elegancies that modern refinement has introduced into the dwellings..."

"[T]he causes which produce smoke in rooms... may be all reduced to one of the three following general classes: 1. A faulty construction of the tube, vent, or chimney itself; 2. To some fault in the other parts of the building, and a wrong position of the chimney with respect to these; or, 3. To an improper situation of the house with respect to external objects."

"The earth is every where surrounded with a great body of air, that is called the atmosphere. This air is a thin elastic fluid, possessing some qualities peculiar to itself, but subjected in general to the same physical laws with other fluids; and of consequence it hath a constant tendency to preserve an exact equilibrium in all its parts; so that if at any time the weight of it at one place is diminished, the heavier air rushes from all sides towards that point, till the equilibrium be again restored."

"Many are the causes that may tend to destroy this equilibrium of the atmosphere; but the only one that it imports our present discussion to explain the effects of, is ."

"When heat acts upon the air, it immediately makes it expand to a great degree, so as that the same quantity of it occupies a much larger space than formerly. Hence... where a fire is kindled, the air immediately contiguous to it will be heated, and of consequence rarefied, and made lighter..."

"[A]s it is an invariable rule among all fluids, that those which are lightest rise upwards, and at length swim upon the top of such as are more weighty... so... that when any particles of the same fluid are... rendered lighter, or more weighty, than other parts... they either rise to the top, and give place to the more dense and weighty parts of it, or sink to the bottom, and force the warmer fluid to the surface."

"It is owing to this cause that the water at the top of a caldron, before it begins to boil, is always as warm, or warmer, than what is below:—for the particles of water that touch the bottom are no sooner acted upon by the heat below, than they become warmer, and more expanded, than those immediately above them, and therefore rise directly upwards, and give place to denser cold particles, which are forced in their turn to ascend in like manner towards the top."

"In the same manner... when the air contiguous to a fire is heated... it is immediately expanded very much; and therefore instantly rises upwards, till it reaches the higher regions of the atmosphere, or is cooled by gradually mixing with the denser air it meets with in its ascent:—and as its place contiguous to the fire is immediately occupied by the cold dense air around it, which rushes from every side towards that point, it is heated and rarefied in its turn, and ascends in the same manner, carrying the smoke that rises from the burning body along with it."

"It is in this manner that the constant suction of air towards every fire is produced; and from this cause proceeds the continual tendency of smoke to ascend from the surface of the earth, unless where some circumstance interrupts the course of nature."

"[M]en... disccovered, that when the fire was surrounded with a wall to any considerable height, the motion of the wind was interrupted by it, and the smoke allowed to rise upwards till it reached the top of the building.—The free ascent of this disagreeble vapour... was promoted by the addition of a roof... Hence... in every part of the globe the first and most simple huts... are circular buildings, with a conical roof; in the middle of which, for the most part, is left a hole for the emission of the smoke; the fire having been placed in the centre of the building immediately below the opening, which served instead of a window, as well as a vent-hole for the smoke."

"[A]s luxury encreased, and the elegant arts became more common... fire places were contracted to a narrower size.——The grate, instead of being placed in the middle of a large area, with seats around it, was pushed close to the back wall. The width of the opening of the vent, was found to be sufficient if it contained the whole of the grate;—and as the fire warmed the room more effectually when it came well forward, the grate was brought as far into the apartment as could be done.—The pipe of the chimney was contracted to such dimensions as to admit of being contained within the thickness of an ordinary wall, and reduced to that elegant and commodious tube now known by the name of chimney."

"[H]igh [longer] chimneys... have a greater suction of air, and are less liable to vent ill, than low ones, and this is one principal reason why in the same house the chimneys in the garrets, and the higher stories, are more apt to vent ill, than those on the floor, where the chimneys are of necessity longer. A smoky chimney, therefore, may sometimes be cured, merely by raising it higher..."

"A chimney may not only be defective by having the mantle too high, or by being too wide from side to side, but also by being too deep between the fore-side and the back, as is often the case in very old houses. In this case, the distance between the fire and the mantle is so great, that much air passes up without being sufficiently rarefied... This fault may be sometimes cured, by bringing the grate a little forward, which, by making the fire act more powerfully upon the mantle, rarefies the air more in its passage."

"[W]hen the grate is brought forward, there is a great vacancy left between it and the back of the chimney, so... air passes under the grate, and ascends behind it very little rarefied; so... there will be as much lost in this way as will be gained in the other: and as there is not enough of heated air... to make the vapour ascend with rapidity, they are often choaked with thick fuliginous vapours hanging in them, almost in equilibrio with the rest of the atmosphere, so that the least puff of wind beats them down the chimney, and pushes the smoke into the room; whereas, when it is far back, it is driven down upon the hearth, and rises upwards again when the gust is over, and a great deal of it is catched within the mantle as it rises, which in the other case would have been dispersed through the room."

"When this is the case the most effectual method... is, to bring the grate forward till the forepart of it is immediately under the inner edge of the mantle; then build up the vacancy at the back of it, the whole width of the fire-place from side to side, raising it perpendicularly till it is as high as the back of the grate, and then bending it forward towards the mantle, as... fig 4. When it is as high as the workman can reach, let it be suddenly turned backward again, sloping a little upward... then fit a sheet of milled iron to the inside of the mantle, making it slant a little upward toward the back... a small distance above the new... masonry, and extending within a few inches of the back wall... By this construction all the air that enters into the chimney is made to pass immediately above the fire, between it and the heated iron... as the back of the fire-place is bent a little forward above the grate... the heat is likewise reflected into the room with the greater force... [I]f the smoke is accidentally beat down the chimney by a sudden gust of wind, it will be catched by the sheet of Iron, and prevented from coming into the room."

"[Y]ou desire me to give you... my thoughts upon the Construction and Use of Chimneys... I embrace willingly this leisure... to comply... as it will not only fhew my regard to... a friend, but may... be of some utility to others; the doctrine of chimneys appearing not to be as yet generally well understood, and mistakes respecting them being attended with constant inconvenience, if not remedied; and with fruitless expence, if the true remedies are mistaken."

"Having lit a pipe of tobacco, plunge the stem to the bottom of a decanter half filled with cold water; then putting a rag over the bowl, blow through it, and make the smoke descend in the stem of the pipe, from the end of which it will rise in bubbles through the water; and being thus cooled will not afterwards rise to go out through the neck of the decanter, but remain spreading itself, and resting on the surface of the water. This shews that smoke is really heavier than air; and that it is carried upwards only when attached to, or acted upon, by air that is heated, and thereby rarefied and rendered specifically lighter than the air in its neighbourhood."

"Smoke being rarely seen but in company with heated air, and its upward motion being visible, though that of the rarefied air that drives it is not so, has naturally given rise to... error."

"[A]ir is a which has weight as well as others, though about eight hundred times lighter than water; that heat makes the particles of air recede from each other and take up more space, so that the same weight of air heated will have more bulk [volume] than equal weights of cold air which may surround it, and in that case must rise, being forced upwards by such colder and heavier air, which presses to get under it, and take its place."

"That air is so rarefied or expanded by heat, may be proved to... by a lank blown bladder, which laid before a fire will soon swell, grow tight, and burst."

"Another experiment may be, to take a glass tube... open at both ends, and fixed upright on legs, so that it need not be handled, for the hands might warm it: at the end of a quill, fasten five or six inches of the finest light filament of silk, so that it may be held either above the upper end of the tube or under the lower end, your warm hand being at a distance by the length of the quill. If there were any motion of air through the tube, it would manifest itself by its effect on the silk [Fig. I]; but if the tube and the air in it are of the same temperature with the surrounding air, there will be no such motion. ...Warm the tube, and you will find as long as it continues warm, a constant current of air entering below and passing up through it, till discharged at the top; because the warmth of the tube... rarefies that air, and makes it lighter than the air without, which therefore presses in below, forces it upwards, follows and takes its place, and is rarefied in its turn."

"[N]o form of the funnel of the chimney has any share in its operation or effect respecting smoke, except its height. The longer the funnel if erect, the greater its force when filled with heated and rarefied air, to draw in below and drive up the smoke (if one may in compliance with custom use the expression draw), when in fact it is the superior weight of the surrounding atmosphere that presses to enter the funnel below, and so drives up... the smoke and warm air..."

"I have been... particular in explaining these first principles, because for want of clear ideas respecting them, much fruitless expence has been occasioned... whole stacks having been pulled down and rebuilt with funnels of different forms, imagined more powerful in drawing smoke, but having still the same height and the same opening below, have performed no better than their predecessors."

"What is it then which makes a smoky chimney..? The causes of this effect which have fallen under my observation, amount to nine..."

"Smoky chimneys in a new house are [as] such frequently from mere want of air. The workmanship of the rooms being all good... true and tight... The doors and the sashes too, being worked with truth, shut with exactness so that the room is as tight as a snuff-box."

"Now, if smoke cannot rise... unless other air be admitted to supply its place; and if therefore no current of air enter the opening of the chimney, there is nothing to prevent the smoke coming out into the room."

"If... a column of air, equal to the content of the funnel, must be discharged, and an equal quantity supplied from the room below; it will appear absolutely impossible that this operation should go on if the tight room is kept shut: for were there any force capable of drawing constantly so much air out of it, it must soon be exhausted, like the receiver of an air-pump, and no animal could live in it."

"Those therefore who stop every crevice in a room to prevent the admission of fresh air, and yet would have their chimney carry up the smoke, require inconsistencies, and expect impossibilities."

"I have seen the owner of a new house in despair, and ready to sell it for much less than it cost, conceiving it uninhabitable, because not a chimney in any one of its rooms would carry off the smoke, unless a door or window were left open."

"Much expence has... been made to alter and amend new chimneys which had really no fault: in one house... of a nobleman in Westminster, that expence amounted to... three hundred pounds... and after all, several... alterations were ineffectual, for want of understanding the true principles."

"When you find... that opening the door or a window enables the chimney to carry up all the smoke, you may be sure that want of air from without was the cause of its smoking: I say from without, to guard you against a common mistake of those who may tell you, the room is large, [and] contains abundance of air sufficient to supply any chimney... These reasoners are ignorant, that the largeness of a room, if tight, is... of small importance, since it cannot part with a chimneyful of its air, without occasioning so much vacuum..."

"It appearing plainly... that some of the outward air must be admitted, the question will be, How much is absolutely necessary? ...To discover this quantity, shut the door gradually, while a middling fire is burning, till... the smoke begins to come out into the room; then open it a little, till you perceive the smoke comes out no longer: there hold the door, and observe the width of the open crevice... thence... your room requires an entrance for air equal in area.. I have found ...thirty-six square inches, to... serve for most chimneys."

"High funnels, with small and low openings, may indeed be supplied through a less space [in area]; because... the force of levity being greater in such funnels, the cool air enters the room with greater velocity, and consequently more enters in the same time. This, however, has its limits..."

"It remains then to be considered, how and where this necessary quantity of air from without is to be admitted, so as to be least inconvenient. For, if... the air proceeds directly to the chimney, and... comes cold to your back and heels, as you sit before your fire you feel the... inconvenience."

"Various have been the contrivances to avoid this: such as bringing in fresh air through pipes, in the jams of the chimney, which, pointing upwards, should blow the smoke up the funnel; opening passages into the funnel above, to let in air for the same purpose. But these produce an effect contrary to that intended; for, as it is the constant current of air passing from the room through the opening of the chimney into the funnel, which prevents the smoke coming out into the room, if you supply the funnel by other means, or in other ways, with the air it wants, and especially if that air be cold, you diminish the force of that current, and the smoke, in its efforts to enter the room, finds less resistance."

"The wanted air must... indispensibly be admitted into the room to supply what goes off through the opening of the chimney. M. Gauger... proposes, with judgment, to admit it above the opening of the chimney; and to prevent inconvenience from its coldness, he directs its being made to pass in its entrance through winding cavities made behind the iron back and sides of the fire-place; and under the iron hearth-plate; in which cavities it will be warmed, and even heated, so as to contribute much, instead of cooling, to the warming of the room. This invention is excellent in itself, and may be used with advantage in building new houses; because the chimneys may then be so disposed as to admit conveniently the cold air to enter such passages: but, in houses built without such views, the chimneys are often so situated as not to afford that convenience, without great and expensive alterations. Easy and cheap methods, though not quite so perfect in themselves, are of more general utility; and such are the following:"

"Few can imagine the difference of climate between the upper and lower parts of such a room, who have not tried it by the thermometer, or by going up a ladder till their heads are near the ceiling. It is then among this warm air that the wanted quantity of outward air is best admitted."

"This may be easily done by drawing down about an inch the upper sash of a window; or, if not moveable, by cutting such a crevice through its frame... it will be well to place a thin shelf... to conceal the opening; and sloping upwards, to direct the entering air... In some houses, the air may be admitted by such a crevice... near the ceiling and over the opening of the chimney. ...[T]he entering cold air will there meet with the warmest rising air from before the fire, and be soonest tempered by the mixture. The same kind of shelf should also be placed here."

"Another way... is to take out an upper pane of glass in one of your sashes: set it in a tin frame, giving it two springing angular sides, and then replacing it with hinges below [Fig. 2], on which it may be turned to open more or less above. ...By drawing this pane in more or less, you may admit... air... Its position will naturally throw that air up and along the ceiling."

"A second cause of the smoking of chimneys is, their openings in the room being too large... Architects... have no other ideas of proportion in the opening of a chimney, than what relate to symmetry and beauty... while its true proportion, respecting its function and utility, depends on quite other principles... The proportion then to be regarded, is what relates to the height of the funnel. For... funnels in the different stories of a house are necessarily of different heights or lengths... [T]he openings of the longest funnels may be larger, and that those of the shorter funnels should be smaller. For if there be a large opening to a chimney that does not draw strongly, the funnel may... be furnished with the air it demands by a partial current... on one side of the opening... the other side free of any opposing current, may permit the smoke to issue there into the room."

"Much... of the force of draft in a funnel depends on the degree of rarefaction in the air it contains; and that depends on the nearness to the fire... in entering the funnel. If it can enter far from the fire on each side, or far above the fire in a [too] wide or high opening, it receives little heat in passing by the fire, and the contents of the funnel is by that means less different in levity from the surrounding atmosphere, and its force in drawing consequently weaker."

"Hence if too large an opening be given to chimneys in upper rooms, those rooms will be smoky."

"On the other hand, if too small openings be given to chimneys in the lower rooms, the entering air operating too directly and violently on the fire; and afterwards strengthening the draft as it ascends the funnel, will consume the fuel too rapidly."

"If you suspect that your chimney smokes from the too great dimension of its opening, contract it by placing moveable boards so as to lower and narrow it gradually, till you find the smoke no longer issues into the room. The proportion so found will be that which is proper... and you may employ the bricklayer or mason to reduce it accordingly."

"[I]n building new houses... I would have the openings in my lower rooms about thirty inches square and eighteen deep, and those in the upper only eighteen inches square and not quite so deep; the intermediate ones diminishing in proportion as the height of funnel diminished. ...The same depth is nearly necessary to all, the funnels being all made of a size proper to admit a chimney-sweeper."

"If in large and elegant rooms custom or fancy should require the appearance of a larger chimney, it may be formed of expensive marginal decorations, in marble, &c. In time, perhaps, that which is fittest in the nature of things may come to be thought handsomest."

"But at present, when men and women in different countries shew themselves dissatisfied with the forms God has given to their heads, waists, and feet, and pretend to shape them, more perfectly, it is hardly to be expected that they will be content always with the best form of a chimney. And there are some, I know, so bigotted to the fancy of a large noble opening, that, rather than change it, they would submit to have damaged furniture, fore eyes, and skins almost smoked to bacon."

"The plague of a smoking Chimney is proverbial; but there are many other very great defects in open Fire-places, as... commonly constructed... which, being less obvious, are seldom attended to; and there are some of them... fatal in their confequences... and... cost the lives of thousands every year... By a cause which might be so easily removed!—by a cause whose removal would tend to promote comfort and convenience in so many ways."

"There are various causes by which Chimnies may be prevented from carrying smoke; but there are none that may not easily be discovered and completely removed."

"Those who will take the trouble to consider the nature and properties of elastic s,—of air,—smoke,—and vapour,—and to examine the laws of their motions, and the necessary consequences of their being rarified by heat, would perceive that it would be as much a miracle if smoke should not rise in a Chimney, (all hindrances to its ascent being removed,) as that water should refuse to run in a syphon, or to descend in a river."

"The whole mystery, therefore, of curing smoking Chimnies is comprised in this simple direction,—find out and remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the Chimney; or rather, to speak more accurately, which prevents its being forced up the Chimney by the pressure of the heavier air of the room."

"[T]hat cause which will... almost universally be found to operate, is one which it is always very easy to discover, and as easy to remove,—the bad construction of the Chimney in the neighbourhood of the Fire-place."

"I have never been obliged, except in one... instance, to have recourse to any other method of cure than merely reducing the Fire-place and the throat of the Chimney, or that part of it which lies immediately above the Fire-place, to a proper form, and just dimensions."

"[O]f above an hundred and fifty Fire-places which have been altered in this city, under my direction, within these last two months, there is not one which has not answered perfectly well. ...the saving of fuel, arising from these improvements of Fire-places, amounts in all cases to more than half, and in many cases to more than two thirds of the quantity formerly consumed."

"Now as the alterations in Fire-places which are necessary may be made at a very trifling expence... as no iron work, but merely a few bricks and some mortar, or a few small pieces of fire-stone, are required; the improvement in question is very important, when considered merely with a view to economy; but it should be remembered, that not only a great saving is made of fuel by the alterations proposed, but that rooms are made much more comfortable, and more salubrious;—that they may be more equally warmed, and more easily kept at any required temperature;—that all draughts of cold air from the doors and windows towards the Fire-place, which are so fatal to delicate constitutions, will be completely prevented;—that in consequence of the air being equally warm all over the room, or in all parts of it, it may be entirely changed with the greatest facility, and the room completely ventilated, when this air is become unfit for respiration, and this merely by throwing open for a moment a door opening into some passage from whence fresh air may be had, and the upper part of a window; or by opening the upper part of one window and the lower part of another."

"And as the operation of ventilating the room, even when it is done in the most complete manner, will never require the door and window to be open more than one minute; in this short time the walls of the room will not be sensibly cooled, and the fresh air which comes into the room will, in a very few minutes, be so completely warmed by these walls that the temperature of the room, though the air in it be perfectly changed, will be brought to be very nearly the same as it was before the ventilation."

"As long as any fire is kept up in the room, there is so considerable a current of air up the Chimney, notwithstanding all the reduction that can be made in the size of its throat, that the continual change of air in the room which this current occasions will, generally, be found to be quite sufficient for keeping the air in the room sweet and wholesome..."

"Those who have any doubts respecting the very great change of air or ventilation which takes place each time the door of a warm room is opened in cold weather, need only set the door... wide open for a moment, and hold two lighted candles in the door-way, one near the top of the door, and the other near the bottom... The violence with which the flame of that above will be driven outwards, and that below inwards by the two strong currents of air which, passing in opposite directions, rush in and out of the room at the same time, will [convince them] that the change of air which actually takes place must be very considerable... and these currents will be stronger, and consequently the change of air greater, in proportion as the difference is greater between the temperatures of the air within the room and of that without."

"The great fault of all the open Fire-places, or Chimnies, for burning... an open fire, now in common use, is, that they are much too large; or rather it is the throat of the Chimney or the lower part of its open canal, in the neighbourhood of the mantle, and immediately over the fire, which is too large. This opening has hitherto been left larger than otherwise it probably would have been made, in order to give a passage to the Chimney-sweeper; but I shall show... how a passage for the Chimney-sweeper may be contrived without leaving the throat of the Chimney of such enormous dimensions as to swallow up and devour all the warm air of the room, instead of merely giving a passage to the smoke and heated vapour which rise from the fire, for which last purpose alone it ought to be destined."

"I shall endeavour to write in such a manner as to be easily understood by those who are most likely to profit by the information I have to communicate, and consequently most likely to assist in bringing into general use the improvements I recommend."

"As the immoderate size of the throats of Chimnies is the great fault of their construction, it is this fault which ought always to be first attended to in every attempt which is made to improve them; for... if the opening left for the passage of the smoke is larger than is necessary for that purpose, nothing can prevent the warm air of the room from escaping through it; and whenever this happens, there is not only an unnecessary loss of heat, but the warm air which leaves the room to go up the Chimney being replaced by cold air from without, the draughts of cold air... cannot fail to be produced in the room..."

"[A]s the smoke and hot vapour which rise from a fire naturally tend upwards, the proper place for the throat of the Chimney is... perpendicularly over the fire."

"But ...how far above the burning fuel... ought [the throat] to be placed."

"As the smoke and vapour which ascend from burning fuel rise in consequence of their being rarified by heat, and made lighter than the air of the surrounding atmosphere; and as the degree of their rarefaction, and consequently their tendency to rise, is in proportion to the intensity of their heat; and... as they are hotter near the fire than at a greater distance from it, it is clear that the nearer the throat of a Chimney is to the fire, the stronger will be... its draught, and the less danger there will be of its smoking."

"But on the other hand, when... this strong draught is occasioned by the throat of the Chimney being very near the fire... the draught... may become so strong, as to cause the fuel to be consumed too rapidly. There are likewise several other inconveniences which would attend the placing of the throat of a Chimney very near the burning fuel."

"[T]he height of the throat... will be determined by the height of the mantle. It can hardly be made lower than the mantle; and it ought always to be brought down as nearly upon the level with the bottom of it as possible."

"If the Chimney is apt to smoke, it will sometimes be necessary either to lower the mantle or to diminish the height of the opening of the Fire-place, by throwing over a flat arch, or putting in a straight piece of stone from one side of it to the other, or... building a wall of bricks, supported by a flat bar of iron, immediately under the mantle."

"Nothing is so effectual to prevent Chimnies from smoking as diminishing the opening of the Fire-place in the manner here described, and lowering and diminishing the throat of the Chimnney; and... a perfect cure may be effected by these means alone, even in the most desperate cases."

"[W]hen the construction of the Chimney is very bad... or... very unfavourable to the ascent of the smoke, and especially when both these disadvantages exist... it may... be necessary to diminish the opening of the Fire-place, and particularly to lower It, and also to lower the throat... more than might be wished: but... this can produce no inconveniences to be compared with that greatest of all plagues, a smoking Chimney."

"The position of the throat... being determined, the next points... are its size and form, and the manner in which it ought to be connected with the Fire-place below, and with the open canal of the Chimney above."

"Now the design of a Chimney Fire being... to warm a room... with the smallest expence of fuel... and... that... the air of the room be preserved... pure... fit for respiration, and free from smoke and... disagreeable smells."

"[H]eat which is generated in the combustion of the fuel exists under two... distinct... forms. One... is combined with the smoke, vapour, and heated air which rise from the burning fuel, and goes off with them into the... atmosphere; ...the other part, which appears to be uncombined, or... supposed, combined only with light, is sent off from the fire in rays in all possible directions."

"[I]t is... probable that the combined heat can only be communicated to other bodies by actual contact with the body with which it is combined; and... the rays... communicate or generate heat only when and where they are stopped or absorbed. ...[T]hey seem to bear a great resemblance to the solar rays. ...I must not enter too deeply into... the nature and properties of... radiant heat."

"What proportion does the radiant heat bear to the combined heat? ...[T]he quantity of heat which goes off combined with the smoke, vapour, and heated air is much more considerable, perhaps three or four times greater... And yet, small as the quantity is of... radiant heat, it is the only part... ever employed... in heating a room. The whole of the combined heat escapes by the Chimney, and is totally lost; and... no part of it could ever be brought into a room from an open Fire-place, without bringing along... the smoke..."

"There is, however, one method by which combined heat... may be made to assist in warming a room... by making it pass through something analogous to a German stove, placed in the Chimney above the fire."

"[A]s it is the radiant heat alone which can be employed in heating a room, it becomes an object of much importance to determine how the greatest quantity of it may be generated... and how the greatest proportion possible of that generated may be brought into the room."

"When the fire burns bright, much radiant heat will be sent off from it; but when it is smothered up, very little will be generated... and the combustion being very incomplete, a great part of the inflammable matter of the fuel being merely rarefied and driven up the Chimney without being inflamed, the fuel will be wasted... And hence it appears of how much importance it is, whether.. with a view to economy... cleanliness, comfort, and elegance, to pay due attention to the management of a Chimney Fire."

"Chimnies so often smoke when too large a quantity of fresh coals is put upon the fire. So many coals should never be put on the fire at once as to prevent the free passage of the flame between them. In short, a fire should never be smothered; and when proper attention is paid to the quantity of coals put on, there will be very little use for the poker; and this circumstance will contribute very much to cleanliness, and to the preservation of furniture."

"Now as the rays which are thrown off from burning fuel have this property in common with light, that they generate heat only when and where they are stopped or absorbed, and also in being capable of being reflected without generating heat at the surfaces of various bodies, the knowledge of these properties will enable us to take measures, with the utmost certainty, for producing the effect required... bringing as much radiant heat as possible into the room. This must be done, first, by causing as many as possible of the rays, as they are sent off from the fire in straight lines, to come directly into the room; which can only be effected by bringing the fire as far forward as possible, and leaving the opening of the Fire-place as wide and as high as can be done without inconvenience; and secondly, by making the sides and back of the fire-place of such form, and constructing them of such materials, as to cause the direct rays from the fire, which strike against them, to be sent into the room by reflection in the greatest abundance."

"[T]he best form for the vertical sides of a Fire-place, or the covings... is that of an upright plane, making an angle with the plane of the back of the Fire-place, of about 135 degrees.—According to the present construction of Chimnies this angle is 90 degrees... a right angle; but as... the two sides or covings of the Fire-place are parallel to each other, it is evident that they are very ill contrived for throwing into the room by reflection the rays..."

"As the object... is to bring radiant heat into the room... that material is best for the construction of a Fire-place which reflects the most, or which absorbs the least of it; for that heat which is absorbed cannot be reflected. ...[W]e have only to find out ...what bodies acquire least heat when exposed to the direct rays of a clear fire ...And hence it appears that iron, and ...metals off all kinds, which ...grow very hot when exposed to the rays ...are to be reckoned among the very worst materials ...to employ in the construction of Fire-places."

"The best materials... are fire-stone, and common bricks and mortar. Both... are, fortunately, very cheap..."

"When bricks are used they should be covered with a thin coating of plaster, which, when it is become perfectly dry, should be white-washed. The fire-stone should likewise be white-washed... and every part of the fire-place, which is not exposed to being foiled and made black by the smoke, should be kept as white and clean as possible. As white reflects more heat, as well as more light than any other colour, it ought always to be preferred for the inside of a Chimney Fire-place; and black, which reflects neither light nor heat, should be most avoided."

"[T]he quantity of radiant heat thrown into the room is diminished;—and it is easy to show that almost the whole of that absorbed by the metal is ultimately carried up the Chimney by the air, which, coming into contact with this hot metal, is heated and rarefied by it, and... goes off with the smoke; and as no current of air ever sets from any part of the opening of a Fire-place into the room, it is impossible to conceive how the heat existing in the metal composing any part of the apparatus of the Fire-place, and situated within its cavity, can come, or be brought into the room."

"This difficulty may be in part removed, by supposing... that the heated metal sends off in rays... even when it is not heated red hot; but still, as it never can be admitted that the heat, absorbed by the metal and afterwards thrown off by it in rays, is increased by this operation, nothing can be gained by it; and as much must necessarily be lost... to the air in contact with it, which... always makes its way up the Chimney, and flies off into the atmosphere, the loss of heat attending the use of it is too evident..."

"There is, however, in Chimney Fire-places... one essential part, the grate, which cannot well be made of any thing else but iron..."

"If it should be necessary to diminish the opening of a large Chimney in order to prevent its smoking, it is much more simple, œconomical, and better in all respects, to do this with marble, fire-stone, or even with bricks and mortar, than to make use of iron, which... is the very worst material... for that purpose; and as to registers, they not only are... unnecessary, where the throat of a Chimney is properly constructed, and of proper dimensions, but in that case would do mach harm. If they act It all, it must be by opposing their flat surfaces to the current of rising smoke in a manner which cannot fail to embarrass and impede its motion. But... the passage of the smoke through the throat of a Chimney ought to be facilitated as much as possible in order that it may be enabled to pass by a small aperture."

"Register-stoves have often been found to be of use, but because the great fault of all Fire-places constructed upon the common principles being the enormous dimensions of the throat of the Chimney, this fault has been in some measure corrected by them; but I will venture to affirm, that there never was a Fire-place so corrected that would not have been much more improved, and with infinitely less expence by the alterations here recommended..."

"All Chimney Fire-places, without exception... and even those which do not smoke, as well as those which do, may be greatly improved by making the alterations... here recommended; for it is by no means merely to prevent Chimnies from smoking that these improvements are recommended, but it is also to make them better in all respects... and when the alterations proposed are properly executed, which may very easily be done with the assistance of the following plain and simple directions, the Chimnies will never fail to answer... even beyond expectation. The room will be heated much more equally and more pleasantly with less than half the fuel used before, the fire will be more cheerful and more agreeable; and the general appearance of the Fire-place more neat and elegant, and the Chimney will never smoke."

"I know of no disadvantage... that attends the Fire-places constructed upon the principles here recommended."

"By the throat of a Chimney, I mean the lower extremity of its canal, where it unites with the upper part of its open Fire-place.—This throat is commonly found about a foot above the level of the lower part of the mantle, and it is sometimes contracted to a smaller size than the rest of the canal of the Chimney, and sometimes not."

"The breast of a Chimney is that part of it which is immediately behind the mantle.—It is the wall which forms the entrance from below into the throat of the Chimney in front, or towards the room. — It is opposite to the upper extremity of the back of the open Fire-place, and parallel to it;—in short it may be said to be the back part of the mantle itself."

"The width of the throat of Chimney... is taken from the breast of the Chimney to the back, and its length is taken at right angles to its width, or in a line parallel to the mantle..."

"The bringing forward of the fire into the room, or rather bringing it nearer to the front of the opening of the Fire-place;—and the diminishing of the throat of the Chimney, being two objects principally had in view in the alterations... here recommended... both... may be attained merely by bringing forward the back of the chimney."

"The only question... is, how far [the fire] should be brought forward?—The answer... bring it forward as far as possible, without diminishing too much the passage which must be left for the smoke."

"Now as this passage, which, in its narrowest part, I have called the throat of the Chimney, ought... to be immediately, or perpendicularly over the Fire, it is evident that the back of the Chimney must always be built perfectly upright.—To determine therefore the place for the new back, or how far precisely it ought to be brought forward, nothing more is necessary that to ascertain how wide the throat of the Chimney to be left, or what trace must be left between the top of the breast of the Chimney, where the upright canal of the Chimney begins, and the new back of the Fire-place carried up perpendicularly to that height."

"In the course of my numerous experiments upon Chimnies I have taken much pains to determine the width proper to be given to this passage, and I have found that, when the back of the Fire-place is of the proper width, the best width for the throat of the Chimney, when the Chimney and the Fire-place are of the usual form and size, is four inches. Three inches might sometime answer, especially where the Fire-place is very small, and the Chimney good, and well situated; but as it is... of much importance to prevent those accidents... putting too many coals at once upon the fire... when the throats of Chimnies were... very narrow..."

"It may... appear extraordinary... that Fire-places of such different sizes should all require the throat of the Chimney to be of the same width; but... the capacity of the throat of a Chimney does not depend on its width alone, but on its width and length taken together; and that in large Fire-places, the width of the back, and consequently the length of the throat of the Chimney, is greater than in those which are smaller..."

"In Fire-places as they are now commonly constructed, the back is of equal width with the opening of the Fire-place in front;-—but this... is faulty on two accounts.— First... the sides... or covings... are parallel to each other, and consequently ill-contrived to throw out into the room the heat they receive from the fire in the form of rays;—and secondly, the large open corners which are formed by making the back as wide as the opening of the Fire-place in front occasion eddies of wind, which frequently disturb the fire, and embarrass the smoke in its ascent in such a manner as often to bring it into the room."

"Both these defects may be entirely remedied by diminishing the width of the back of the Fire-place.—The width which, in most cases, it will be best to give it, is one third of the width of the opening of the Fire-place in front."

"It will frequently happen that the back of a Chimney must be made wider than... the rule here given... This may be, either to accommodate the Fire-place to a stove... already on hand... or for other reasons... with no considerable inconvenience.—It will always be best however to conform to it as far as circumstances will allow."

"Where a Chimney is designed for warming a room of a middling size, and where the thickness of the wall of the Chimney in front, measured from the front of the mantle to the breast of the Chimney, is nine inches, I should set off four inches more for the width of the throat of the Chimney, which supposing the back of the Chimney to be built upright, as it always ought to be, will give thirteen inches for the depth of the Flre-place measured upon the hearth, from the opening of the Fire-place in front, to the back.—In this case thirteen inches would be a good size for the width of the back; and three times thirteen inches, or thirty-nine inches, for the width of the opening of the Fire-place in front; and the angle made by the back of the Fire-place and the sides of it, or covings, would be just 135 degrees, which is the best position they can have for throwing heat into the room."

"I will suppose that in altering such a Chimney it is found necessary, in order to accommodate the Fire-place to a grate or stove already on hand, to make the Fire-place sixteen inches wide.—In that case, I should merely increase the width, of the back, to the dimensions required, without; altering the depth of the Chimney, or increasing the width of the opening of the Chimney in front.—The covings... would be somewhat reduced in their width... and their position... would be a little changed; but these alterations would produce no bad effects of any considerable consequence, and would be much less likely to injure the Fire-place..."

"Should the opening of the Chimney be too narrow, which however will very seldom be found to be the case, it will, in general, be advisable to let it remain as it is, and to accommodate the covings to it, rather than to attempt to increase its width, which would be attended with a good deal of trouble, and probably a considerable expence."

"[T]he points of the greatest importance... in altering Fire-places upon the principles here recommended, are, the bringing forward the back to its proper place, and making it of a proper width."

"[T]he new back... necessary to build in order to bring the fire sufficiently forward... need never be thicker than the width of a common brick.—I may say the same of the thickness necessary to be given to the new sides, or covings... or if the new back and covings are constructed of stone, one inch and three quarters, or two inches in thickness will be sufficient."

"Whether the new back and covings are constructed of stone, or... bricks, the space between them, and the old back and covings of the Chimney ought to be filled up... with loose rubbish, or pieces of broken bricks, or stones, provided the work be strengthened by a few layers or courses of bricks laid in mortar; but it will be indispensably necessary to finish the work where these new walls end... at the top of the throat of the Chimney, where it ends abruptly in the open canal of the Chimney by a horizontal course of bricks well secured with mortar."

"[W]here the throat of the Chimney has an end... where it enters into the lower part of the open canal of the Chimney, there the three walls which form the two covings and the back of the Fire-place all end abruptly. ...[T]hey should end in this manner for were they to be sloped outward and raised in such a manner as to swell out the upper extremity of the throat of the Chimney in the form of a trumpet, and increase it by degrees to the size of the canal of the Chimney, this manner of uniting the lower extremity of the canal of the Chimney with the throat would tend to assist the winds which may attempt to blow down the Chimney, in forcing their way through the throat, and throwing the smoke backward into the room; but when the throat of the Chimney ends abruptly, and the ends of the new walls form a flat horizontal surface, it will be much more difficult for any wind from above, to find, and force its way, through the narrow passage of the throat..."

"As the two walls which form the new covings... are not parallel... but inclined, presenting an oblique surface towards the front of the Chimney, and as they are built perfectly upright, and quite flat, from the hearth to the top of the throat, where they end... an horizontal section of the throat will not be an oblong square; but its deviation from that form is a matter of no consequence; and no attempts should ever be made, by twisting the covings above, where they approach the breast of the Chimney, to bring it to that form."

"All twists, bends, prominences, excavations, and other irregularities of form, in the covings... never fail to produce eddies in the current of air which is continually passing into, and through an open Fire-place in which a fire is burning;—and all such eddies disturb, either the fire, or the ascending current of smoke, or both; and not unfrequently cause the smoke to be thrown back into the room.—Hence... the covings... should never be made circular, or in the form of any other curve; but always quite flat."

"For the same reason, that is... to prevent eddies, the breast of the Chimney, which forms [the front] side of the throat... or nearest to the room, should be neatly cleaned off, and its surface made quite regular and smooth. This may easily be done by covering it with a coat of plaister, which may be made thicker or thinner in different parts as may be necessary in order to bring the breast of the Chimney to be of the proper form."

"[T]he form of the breast of the Chimney is... of... great importance... The worst form it can have is that of a vertical plane, or upright flat;—and next... worst... is an inclined plane.—Both... cause the current of warm air from the room, which will... sometimes find its way into the Chimney, to cross upon the current of smoke, which rises from the fire, in a manner, most likely to embarrass it in its ascent, and drive it back.— The inclined plane which is formed by a flat register placed in the throat of a Chimney produces the same effects; and this is one reason, among many... which have induced me to disapprove of register stoves."

"The current of air, which, passing under the mantle, gets into the Chimney, should be made gradually to bend its course upwards, by which means it will unite quietly with the ascending current of smoke, and will be less likely to check it, or force it back into the room.—Now this may be effected with the greatest ease and certainty, merely by rounding off the breast of the Chimney or back part of the mantle, instead of leaving it flat, or full of holes and corners; and this... ought always to be done."

"[T]he height to which the new back and covings ought to be carried... will depend not only on the height of the mantle, but also, and more especially, on the height of the breast of the Chimney, or of that part of the Chimney where the breast ends and the upright canal begins.—The back and covings must rise a few inches, five or six... higher than this part, otherwise the throat of the Chimney will not be properly formed;—but I know of no advantages that would be gained by carrying them up still higher."

"Those [grates] whose construction is the most simple, and... the cheapest, are beyond comparison the best, on all accounts.— Nothing being wanted in these Chimnies but merely a grate for containing the coal, and in which they will burn with a clear fire;—and all additional apparatus being, not only useless, but very pernicious, all complicated and expensive grates should be laid aside, and such as are more simple substituted in the room of them."

"And in the choice of a grate, as in every thing else, beauty and elegance may easily be united with the most perfect simplicity.—Indeed they are incompatible with every thing else."

"In modern built houses where the doors and windows are... made to close with such accuracy that no crevice is left for the passage of the air from without... When there is a fire burning... as the air necessary to supply the current up the Chimney where the fire burns cannot be had in sufficient quantities... through the very small crevices of the doors and windows, the air in the room becomes rarefied, not by heat, but by subtraction of that portion of air which is employed in keeping up the fire, or supporting the combustion of the fuel, and in consequence of this rarefaction, its elasticity is diminished, and being at last overcome by the pressure of the external air of the atmosphere, this external air rushes into the room by the only passage left for it... by the open Chimney."

"The most obvious remedy... is to provide for the supply of fresh air necessary for keeping up the fires by opening a passage for the external air into the room by a shorter road than down one of the Chimnies..."

"But Chimnies so circumstanced may very frequently be prevented from smoking even without opening any new passage for the external air, merely by diminishing the draught... up the Chimnies... by altering both Fire-places upon the principles recommended... in the foregoing..."

"Where the top of a Chimney is commanded by high buildings, by clifts, or by high grounds, it will frequently happen, in windy weather, that the eddies formed in the atmosphere by these obstacles will blow down the Chimney, and beat down the Smoke into the room.—This it is true will be much less likely to happen when the throat of the Chimney is contracted and properly formed than when it is left quite open, and the Fire-place badly constructed; but... One of the most simple contrivances that can be made use of, and which in most cases will be found to answer the purpose intended as well or better than more complicated machinery, is to cover the top of the Chimney with a hollow truncated pyramid or cone, the diameter of which above, or opening for the passage of the Smoke, is about 10 or 11 inches. ...[I]ts perpendicular height may be equal to the diameter of its opening above, and the diameter of its opening below equal to three times its height.-—It should be placed upon the top of the Chimney, and it may be contrived so as to make a handsome finish to the brickwork."

"The intention of this contrivance is that the winds and eddies which strike against the oblique surface of these covers may be reflected upwards instead of blowing down the Chimney.—The invention is by no means new, but it has not hitherto been often put in practice.—As often as I have seen it tried it has been found to be of use; I cannot say,. however, that I was ever obliged to have recourse to it, or to any similar contrivance; and if I forbear to enlarge upon the subject of these inventions, it is because I am persuaded that when Chimnies are properly constructed in the neighbourhood of the Fire-place little more will be necessary to be done at the top of the Chimney than to leave it open."

"In lighting a coal fire more wood should be employed than is commonly used, and fewer coals; and as soon as the fire burns bright, and the coals are well lighted, and not before, more coals should be added to increase the fire to its proper size."

"The enormous waste of fuel in London may be estimated by the vast dark cloud which continually hangs over this great metropolis, and frequently overshadows the whole country, far and wide; for this dense cloud is certainly composed almost entirely of unconsumed coal, which having stolen wings from the innumerable fires of this great city has escaped by the Chimnies, and continues to sail about in the air, till having lost the heat which gave it volatility, it falls in a dry shower of extremely fine black dust to the ground, obscuring the atmosphere in its descent, and frequently changing the brightest day into more than Egyptian darkness."

"I never view from a distance, as I come into town this black cloud which hangs over London without wishing to be able to compute the immense number of chaldrons of coals of which it is composed; for could this be ascertained, I am persuaded so striking a fact would awaken the curiosity, and excite the astonishment of all ranks of the inhabitants; and perhaps turn their minds to an object of economy to which they have hitherto paid little attention."

"Though the saving of fuel which will result from the improvements to the forms of Chimney Fire-places here recommended will be very considerable, yet I hope to be able to show in a future Essay, that still greater savings may be made, and more important advantages derived from the introduction of improvements I shall propose in Kitchen Fire-places."

"I hope likewise to be able to show in an Essay on Cottage Fire-places, which I am now preparing for publication, that three quarters, at least, of the fuel which cottagers now consume in cooking their victuals, and in warming their dwellings, may with great ease, and without any expensive apparatus, be saved."

"I was much flattered on my return to England, in September 1798... to find that the improvements in the construction of chimney fire-places, which I had recommended in my Fourth Essay, published... 1796, were coming into use... It has been objected... that they sometimes occasion dust and ashes to come into the room when the fire is stirred. I have examined several fire-places... that have... that fault; but... found... their imperfections have arisen from faults in... construction. Either the grate has been brought out too far into the room, or the opening of the fire-place in front has been left too wide—or too high—or the workman has neglected to lower and to round off the breast of the chimney—or... several of these faults... together..."

"When the throat of a chimney is situated very high up above the mantle, and especially when the mantle and breast of the chimney, or the wall that reposes on the mantle, are very thin, workmen who are employed to alter chimnies, setting about the work with their minds strongly prepossessed with what they consider as the leading principle... that the throat of the chimney should not be more than four inches wide, they are very apt to bring the grate too far forward. In dropping their plumb-line from the breast of the chimney, they do not reach up high enough into the chimney, but take a part of the breast, where it still goes on to slope backwards, for the bottom of the perpendicular canal of the chimney. They also very often commit another fault, not less essential... in neglecting to bring down the throat of the chimney nearer to the fire, when... too high."

"It is likewise very important to "round off the breast of the chimney;" though this... is very often intirely neglected... by workmen..."

"The breast of a chimney should always be rounded off... beginning from the very front of the lower part of the mantle, and ending at the narrowest part of the throat of the chimney, where the breast ends in the front part of the perpendicular canal of the chimney. If the under surface of the mantle is flat and wide, it will be impossible to round off the breast properly; and that circumstance alone renders it indispensably necessary, in those cases, to alter the mantle, or to run under it a thinner piece of stone, or a thin wall of bricks, supported on an iron bar, in order that the breast of the chimney may be brought to be of the proper form, and the throat of the chimney may be brought into its proper situation."

"If the under side of the mantle be left broad and flat... the cloud of dust or light ashes, that rises from a coal fire nearly burnt out, when... violently stirred... with a poker, striking perpendicularly against this flat part... must... be beat back into the room; but when the breast of the chimney is properly rounded off, the ascending cloud of dust and smoke more easily finds its way into the throat of the chimney, and is even directed and assisted in some measure by the warm air of the room that gets under the mantle and is going the same way."

"Another very common fault... in chimney fire-places, that have been altered on what have been called my principles, and which has a direct tendency to bring dust, and even smoke, into the room, is the sloping of the covings too much, and leaving the opening of the fire-place in front too wide. I have said, in my Essay on Chimney Fire-places, that where chimnies are well constructed, and well situated, and have never been apt to smoke, in altering them the covings may be placed at an angle of 135 degrees with the back; but... that they should never exceed that angle, and... bad consequences... must follow from making the opening of a fire-place very wide, when its depth is very shallow..."

"...for chimnies that are apt to smoke, the covings should be placed less obliquely in respect to the back, than in others that have not that fault. But most... workmen... paid little attention to these distinctions and... frequently... and sometimes in fire-places that have been remarkably shallow... the covings have been placed at an angle even more oblique than that above-mentioned."

"Another cause... in bringing dust and smoke into rooms... is the great nicety with which the doors and windows are fitted in their frames, which prevents a sufficient quantity of fresh air from coming into the room, to supply a brisk current up the chimney. ...[A]ll the alterations in fire-places on the common construction, that have been recommended in order to improve them, must tend directly and very powerfully to lessen this evil; but nothing will so completely remedy it as lowering the mantle, and diminishing the width of the fire-place."

"How many fire-places in close rooms have been cured completely of throwing puffs of smoke and dust into the room, merely by placing a register-stove in them? But there is surely nothing peculiar to a register-stove that could enable it to perform such a cure, but merely as it serves to diminish the width and heighth of the opening of the fire-place; and how much easier could this be done with marble, or other stone, or with bricks and mortar... [T]he openings of chimney fire-places are in general certainly too wide and too high and... there is no way of reducing them to a proper size... so cheap, or more effectual..."

"[C]ovings of... fire-places must be placed obliquely, and they must not be constructed of metal; and if the sides and back of the grate be constructed of fire bricks instead of iron, the fire will burn still brighter, and will fend off considerably more radiant heat into the room."

"If in constructing or altering chimney fire-places, the rules laid down in my Essay on that subject are stricty adhered to, chimnies so fitted up will very seldom be found either to smoke, or to throw out dust into the room; and should they be found to have either of these faults, there is a remedy for the evil, as effectual, as it is simple and obvious: Bring down the mantle, and the throat of the chimney lower; and if it should be found necessary, reduce the width of opening of the fire-place in fronts and diminish the obliquity of the covings."

"I am not the inventor of any of those stoves or grates, that have been offered to the public for sale, under my name."

"In building a house an air canal, about twelve or fifteen inches square, in the clear, and open at both ends, may be constructed, in, or near the center of each stack of chimneys; and two branches from this air canal, both furnished with registers, may open... one... into the fire-place, just under the grate, and the other over the fire-place, and near the top of the room, or just under the ceiling... The bottom of this air tube should reach to the ground, where it should communicate freely with the open air of the atmosphere..."

"Those who consider what an immense quantity of air is required to supply the current that sets up the chimney of an open fire place, where there is a fire burning, must perceive what an enormous loss of heat there must be, when all this expence of air is supplied by the warmed air of the room, and that all this warmed air is necessarily and constantly replaced by the cold air from without, which finds its way into the room, by the crevices of the doors and windows. But all this waste of heat, or any part... may be prevented by the scheme proposed, for if the air necessary to the combustion of the fuel, and to the supplying of the current up the chimney, be furnished by the air-tube, the warmed air in the room will remain in its places and as this will in a great measure prevent the cold currents from the crevices of the door and windows, the heat in the room will be the more equable, and consequently the more wholesome and agreeable on that account."

"[B]y a proper use of the two registers, together with a judicious management of the fire, the air in the room may either be made hotter, or colder;—or may be kept at any given temperature—or the room may be most effectually ventilated; and that this change of air may be effected, either gradually or more suddenly."

"[W]e must never forget that it is the room that heats the air, and not the air that heats the room."

"The rays that are sent off from the burning fuel, generate heat, only when and where they are stopped, or absorbed, consequently they generate no heat in the air in the room, in passing through it, because they pass through it, and are not stopped by it, but, striking against the walls of the room, or against any solid body in the room, these rays are there stopped and absorbed, and it is there that the heat found in the room is generated. The air in the room is afterwards heated by coming into contact with these solid bodies. Many capital mistakes have arisen from inattention to this most important fact."

"It is really astonishing how little attention is paid to events which happen frequently, however interesting they may be as objects of curious investigation, or however they may be connected with the comforts and enjoyments of life."

"Things near us, and which are familiar to us, are seldom objects of our meditations."

"How few persons are there who ever took the trouble to bestow a thought on the subject in question, though it is, in the highest degree, curious and interesting."

"It has frequently been a subject of inquiry, whether the ancients were acquainted with chimneys, or open fire-places. In the houses discovered at and , there are no chimneys; they all appear to have been warmed by furnaces and flues."

"[T]hough one or more expressions of ancient authors may appear to allude to a chimney, if the ancients were acquainted with the art of constructing, in mason-work, elevated funnels for conveying away the smoke, it must be allowed, when we consider the many proofs... to the contrary, that they were... extremely rare."

"It is not known at what time chimneys began to be used. The writers of the 14th century seem either to have been unacquainted with chimneys, or to have considered them as the newest invention of luxury."

"That there were no chimneys in the 10th, 12th, and 13th centuries, has been presumed from the terms "ignitegium" [curfew] or "inpritegium" the curfew-bell of the English, and couvrefeu of the French; which seem to intimate, that the people made fires in their houses in a hole or pit in the centre of the floor, under an opening formed in the roof; and when the fire was burned out, or the family went to bed at night, the hole was shut by a cover of wood."

"The oldest certain account of chimneys, is in the year 1347. An inscription at Venice, records... a great many chimneys (molti comini) were thrown down by an earthquake."

"The first chimney-sweepers in Germany came from , , and the neighbouring territories; and these for a long time were the only countries where the cleaning of chimneys was followed as a trade. Hence it is conjectured, that chimneys were invented in Italy."

"[I]n the countries of modern Europe, the use of stoves prevail throughout the north; while in France and Great Britain, open fires are used. In the warm countries of Italy and Spain, there are very few chimneys, and the only method usually practised of tempering the cold, which is sometimes severely felt, is to burn charcoal in portable brasiers."

"A consists of a fire-place, in which the fuel is consumed, and a flue to carry off the smoke and vapour arising from the combustion; thus affording the benefit of the heat of a fire without the inconvenience of its smoke. But these objects were, and still are, very imperfectly attained; a large portion of the fuel being wasted without increasing the warmth of the apartment."

"Dr. Franklin, in 1785, published "Observations on the Cause and Cure of Smoky Chimneys." He has very satisfactorily explained all the usual causes of this defect, and shown their remedies. To this pamphlet succeeded the "Essay" of Count Rumford, in 1796, whose improvements in the construction of fire-places have been very generally adopted. These two works together, form a valuable body of information. They are well known to the public, but it is not so generally known, that exactly a hundred years ago, viz. in the year 1715, Dr. Desagulier published his book, entitled "Fires Improved, being a new method of Building Chimneys, so as to prevent their smoking, &c." which is a translation of a still older work from the French of M. Gauger, which shows that the most, if not all, the principles pointed out by Count Rumford were understood, and are explained by M. Gauger. He also proposed seven different constructions of chimneys, in which there are hollow cavities made by iron plates in the back[,] jambs and hearth, through which plates the heat passing warms the air in those cavities, which is continually coming into the room fresh and warm. This construction had many obvious advantages; but the expense and difficulty attending it, at that early period, discouraged the propagation of the invention. In our own times, however, similar constructions have been brought forward as new, probably without the knowledge of what had been done so long before, and therefore with all the merit of invention."

"[H]aving, in 1742, invented an open stove for the better warming of rooms, and at the same time saving fuel, as the fresh air admitted was warmed in entering, I made a present of the model to Mr. , one of my early friends, who having an iron furnace, found the casting of the plates for these stoves a profitable thing, as they were growing in demand. To promote that demand, I wrote and published a pamphlet, entitled, "An Account of the new-invented Pennsylvania Fire Places; wherein their construction and manner of operation is particularly explained, their advantages above every method of warming rooms demonstrated; and all objections that have been raised against the use of them, answered and obviated, &c." This pamphlet had a good effect; governor Thomas was so pleased with the construction of this stove as described in it, that he offered to give me a patent for the sole vending of them for a term of years; but I declined it, from a principle which has ever weighed with me on such occasions, viz: That as we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously."

"An ironmonger in London, however, assuming a good deal of my pamphlet, and working it up into his own, making some small changes in the machine, which rather hurt its operation, got a patent for it there, and made, as I was told, a little fortune by it. And this is not the only instance of patents taken out of my inventions by others, though not always with the same success; which I never contested, as having no desire of profiting by patents myself, and hating disputes."

"The use of these fire places in very many houses, both here in Pennsylvania, and the neighbouring states, has been, and is, a great saving of wood to the inhabitants."

"[O]f the [15 1/2] millions of tons of coals raised yearly from the mines, not more than [3 1/2] millions are consumed by steam-engines and in manufacturing operations, leaving [11] or [12] millions of tons of fuel to be mismanaged in kitchens and sitting-rooms throughout the country."

"The register-plate was described at the close of the fifteenth century by Alberti... and by others who wrote afterwards. Were this simple and cheap smoke-valve introduced into every cottage chimney, it would save the heat of [5] or [6] millions of tons of coals that is now annually wasted and thrown away."

"Vitruvius... thus describes the construction of the or stove for heating the or sweating room of a bath. The floor is made inclining, so that a ball placed on any part of it would roll towards the fireplace, by which means the heat is more equally diffused in the sweating-chamber. The floor is paved with tiles... and on these are built brick pillars... two feet high, and cemented with clay and hair mixed together. The pillars are placed at such a distance, as will allow tiles to be laid on them to form the ceiling of the hypocaust, and support the pavement of the caldarium. The air to the caldarium, or room over the hypocaust, is admitted through an aperture in the centre of its roof, from which a brazen shield is suspended by chains. By raising and lowering this shield, which opens or shuts the aperture, the heat of the caldarium is regulated. For heating the water to supply the baths, there are to be three caldrons... the arched cavities in which they stand are to be heated by one fire. After such minute instructions how to form the stove in which large quantities of wood were to be consumed, it is singular that he should omit to notice in what way the smoke produced was to be conveyed into the atmosphere. From this silence, it has been inferred that he was ignorant of what Anderson calls "the elegant and commodious tube now known by the name of a chimney.""

"Longlande, in Pierce the Plowman'sVision, feelingly alludes to the change as prompted by a mean and selfish wish to abridge the ancient hospitality observed towards the poor. "Elynge is that halle eche day in the wyke, Ther the lorde ne the lady liketh nat to sitte. Nowe hath eche ryche a reule to eten by hym silve In a privey parlour for pore mennys sake; Or in a chaumbre wyth a chymney, and leve the cheef halle That was mad for melis men to eten inne." The chimneyed chamber was spacious and lofty, and usually formed with a large bay window, looking into the court of the castle."

"The strong hold of Conway is further remarkable for exhibiting another domestic refinement, not found, except at , in any contemporary building. A hearth is recessed into the wall, and has a rising from it for the passage of the smoke into the air. It is true, that after this period, flued fireplaces were sometimes made in rooms that had been erected without them, but the chimney in Conway Castle, and a similar one at Kenilworth [Castle], appear as if they had formed part of the original edifices."

"Leland, in his Itinerary... gives an account of his visit to . ...[H]e says, ..."One thynge I muche notyd in the hawle of Bolton, how chimeneys were conyened by tunnells made on the syds of the walls betwyxt the lights in the hawle, and by this means, and by no covers, is the smoke of the harthe in the hawle wondor strangely conveyed.""

"[P]revious to the erection of this stronghold, the word chimeney is of frequent occurrence. Chaucer in several places speaks of chambers with chimeneys; Longlande we have seen also employs it: and Wiclif, in his translation of the New Testament, in 1380, has the expression, "thei schulen send him into the chymeney of fier." In the poetical vocabulary, "chimeney" appears to be synonymous with "fireplace," or "hearth recess;" and the verbal equivalent to the word in the reformer's Testament is "furnace." Leland, who wrote a century after, in using the word almost defines it. "The chimeneys were conveyed by tunnels;" or, in other words, the fireplace was continued by a tunnel to the top of the building; a description that will accurately fix the meaning of the word when found in writers previous to the Tudor period; for it is quite obvious the chimneys in common use, and with which Leland was acquainted, had no tunnels to convey the smoke from the hearth... His observation, that the smoke from the hearth was not conveyed by "covers," also shows that at the time... covers were common appendages to fireplaces for conveying smoke. What these were, must be guessed... most likely... "canopies" or "pyramids " constructed over a hearth where it was not recessed into the wall, and often also where it was. Underneath this canopy was a hole through the wall for the escape of the smoke..."

"It is hoped that these amusing details will not make the book less interesting to those who seek to become acquainted with the beautiful laws on which warming and ventilation depend; the principle of the latter art being, in fact, identical with that by which nature ventilates our globe—a hot ascending current from the warm regions, while the cooler air streams in at a lower level from the temperate regions."

"[A] great improvement was made in France in fire-places by Louis Savot (born 1579 ; died 1640), a licentiate in the Faculty of Medicine at Paris."

"Savot pointed out the means for curing that domestic plague—a smoky chimney; and, like a true physician, set about investigating the causes of the disease."

"He saw the evils of large chimneys, and the necessity for a due supply of air to the fire. The fire should be proportioned to the size of the chimney, and vice versâ, and smoke may often be prevented by lowering the mantel."

"[Savot] also points out how the chimney may be too long for the fire, or how one large chimney may draw upon another smaller one; and he recommends that the flue be smooth on the inside, to diminish friction."

"To improve the draught of the fire he raised the hearth about 4 inches, and lowered the mantel so as to make the opening of the fire-place about 3 feet high."

"The width between the jambs was reduced to 3 feet; the jambs from the mantel were to be carried up sloping to the waist, or where the flue begins to be of uniform width, and the opening of the fire-place was formed like an arch."

"But, where the fire-place could not be conveniently altered, Savot perforated with small holes a plate of iron, the width and length of which were nearly equal to the hearth, and this was fixed 3 inches above the tiles of the common hearth. On this perforated plate he placed & grill de fer of the same length as the billets to be burned, and raised 9 inches above the plate; the wood was placed on the grate, the charcoal on the perforated plate, and the hearth received the ashes; the air, rising through the small holes, made the charcoal burn briskly, and this so much assisted the burning of the wood, that a rapid draught up the chimney was established, and smoke prevented."

"In Savot's description of the fire-place used to heat the Cabinet des Livres, at the , we have the first recorded attempt at combining the cheerfulness of an open fire with the economy of an enclosed stove. Fig. 15 is a front view, and Fig. 16 a vertical section of this ingenious contrivance."

"The hearth was a thick iron plate placed above the old hearth, with an interval, n, of 3 inches between them. The two sides, or covings of the fire-place, were also formed of thick iron plates, placed 3 inches from the jambs. The space, n, at the back, and the spaces at the sides, communicated with the space, n, under the hearth ; two pipes, or channels, i, communicating with these hollow spaces, opened into the room at c, as shown by the dotted line in the section; these spaces could be closed at pleasure. When the fire was burning, the iron hearth, and the plates which formed the sides or covings, and the back, became very hot. The cold air at the floor, entering by the openings at a, into the space, n, was heated by the hearth, and rising into the spaces at the back and sides, had its temperature further increased; it then entered the channels, i, and escaped at c, thus diffusing an agreeable warmth over the whole room."

"In 1678, Prince Rupert invented a fire-place, so contrived that the draught took a downward direction before entering the flue, as shown in Fig. 18, in which... x is a wall built at a distance of 10 inches from the back of the hearth recess, and carried up to the mantel, where it is terminated by the wall x, thus completely closing all communication between the flue and the room. An opening, a, is made in this wall, 10 inches high, and of the same width as the length of the grate, and its sill is 2 inches above the top rib of the grate. Fixed within the chimney is a plate of iron, i, placed perpendicularly, so as to divide it into two equal parts. To the upper edge of this plate is hinged an iron door, c, as long as the chimney is wide, and this door can be brought into the position c, or into that indicated by the dotted lines at e. The fuel grate stands on the hearth, and is placed nearly in a line with the wall of the room. At the back of the ash-pit is a brick that closes the aperture through which the soot is removed. When the fire is first lighted, the smoke door, c, is pushed back, and when the draught is once established, this door is drawn forward, and the smoke being thus prevented from flowing upwards, reverberates downwards, and passes the lower edge of the division plate, i, and rises between it and the back of the hearth into the chimney flue. In boisterous weather, or with such a fire-place, in an upper room, where the chimney is short, another iron door, r, is hung under the edge of the mantel, in front of the fire-place, and extending the whole width of the opening. Its breadth varies according to circumstances, but it is made so as to reach within 2 inches of the upper bar of the fire-grate, when hanging in the position shown by the dotted lines at s. This converts the fire into a furnace, and the room will, in such case, be "warmer than it would be with a fire four times the size made in a common cradell." When the smoke flows regularly through the aperture, a, this door is thrown back out of use, as at r. In some cases, the ordinary fire-board or fire-cloth was used instead of this door."

"An economical method of heating two rooms by one ...[fireplace] is described by Savot. A plate of iron is made to separate the fire-places of the two adjacent rooms. A fire made on the hearth, a, (Fig. 20), heats the plate, n, and this, in its turn, by its radiation, warms the air in the adjacent room, e, as effectually as a stove would do, provided its flue, i, is properly closed. Or if the second room have no chimney, it may... be warmed by making an opening in the wall... and closing it with an iron plate. When Dr. Franklin was in Paris, he saw an example of this contrivance, and estimated it highly."

"[T]here is one writer, whose inventions have especially served as the type of many a modern fire-place, and at the time of their introduction in 1713, showed a great and sudden advance in the art of warming apartments. It has been said... that the author... was no less a man than the Cardinal Polignac, who, under the assumed name of Gauger, published a treatise, entitled "La Mechanique du Feu, ou l'Art d'en augmenter les effets et d'en diminuer la dépense, contenant le Traité de Nouvelles Cheminées qui echauffent plus que les Cheminées ordinaires, et qui ne sont point sujettes à fumer" [The Mechanics of Fire, or the Art of increasing its effects and reducing its expenditure, containing the Treatise on New Chimneys which heat much more than ordinary Chimneys, and which are not subject to smoking] This treatise was reprinted at Amsterdam in 1714, and a translation of it, by Dr. Desaguliers... was published in London in 1716."

"It is remarkable that, while the open fireplace was one of the earliest contrivances invented to contribute to the health and comfort of man, the upright flue for carrying off the injurious products of combustion should have remained one of the latest."

"Cold air, being heavier than warm, will fall below the latter, and press it upwards to make way for itself. Thus the air in the neighborhood of the fireplace will press the hot smoke up into the chimney-throat. If this throat is only large enough to take the smoke, hot air only will enter the flue, and the draught will be rapid. But if the throat is larger than necessary, that part of the cool air of the room which enters the fireplace and becomes most heated by the fire, and next in buoyancy to the smoke, will, in its turn, be pressed up by the cooler air behind it, and enter the flue alongside of the smoke. Indeed, the entire volume of the air of the room, being warmer than the outside air, will tend to enter the flue with the smoke, so long as there be room provided for its entrance. The heat of the column, and consequently the rapidity of its rise, will therefore be proportionately diminished."

"For this reason the throat of the chimney should be contracted until it is no larger than is sufficient to carry off the products of combustion. A similar contraction throughout the entire length of the flue would be desirable, were it not that an allowance must be made for clogging up by soot, and for the resistance by friction to the passage of the air offered by the rough walls of the flue."

"The first, to recognize and apply this principle was Count Rumford (1796-1802). ...But he is to be blamed for not investigating or at least acknowledging the progress made by his predecessors in this particular. ...[H]owever much good he may have done in improving the form of the chimney-throat, and in calling public attention to the advantages of bevelled over rectangular jambs, he... also did much to discourage any further effort in economizing the waste heat of the smoke, and should therefore be considered as having really done more than any other one man to retard the proper development of the subject."

"[Rumford] complains of the enormous waste of heat, and regrets that no means of saving it can be invented, in the face of the discoveries of both [Louis] Savot and [Nicholas] Gauger. Even his bevelled jambs for better reflecting the rays into the room had long since been recommended by Gauger. They were brought forward as quite new by Rumford. ...In speaking of the waste in unconsumed smoke... [Rumford] gives no way of consuming the smoke, or of alleviating the evil."

"[T]he so-called Rumford stove or fireplace... contracted the area of the fire-chamber, and gave the sides an angle of 135° with the back, or, which is the same thing, of 45° with the front of the fireplace, in order, as he said, to reflect the greatest possible amount of heat into the room. He considered the best proportions for the chimney recess to be when the width of the back was equal to the depth from front to back, and the width of the front or opening between the jambs three times the width of the back. These proportions are used today, and are undoubtedly the best. He objected to the use of iron for these surfaces on account of its great heat-conducting power, which wasted the heat and cooled off the fire; but advocated some non-conducting substance, such as fire-clay. He also objected to circular covings, on the ground that they produced eddies or currents, which would be likely to cause the chimney to smoke."

"But [Rumford's] chief, or perhaps only, real improvement consisted in the reduction of the size of the chimney-throat, and the rounding off of the lower edge of the chimney-breast... to afford less obstruction to the ascent of the smoke. ...This form, as given by Rumford, is, however, still defective. The smallest part of the flue should be at the bottom... so as to prevent the entrance into the flue of unburnt air from the room. ...The back of the fireplace should also incline forwards, as shown, in order to increase its radiating effect..."

"The simple and earnest style of Count Rumford's essays, the substantial nature of his acknowledged improvement, the facility with which it could be tested, and the enthusiasm with which he urges its importance, the detailed directions he gives for the guidance of the builder, and the liberality with which he offered the free use of his invention and services to the public,—all tended to make a permanent impression, and not only to give the precedence over all others, but even to place the latter altogether in the shade. So much [so] that, though infinitely more important as tending to improve the ventilation of the apartment and the draught of chimney, as well as to save the waste heat of the fuel, they were almost forgotten, and, so far as the mass of the public is concerned, remain so... to the present..."

"So great was the influence of Count Rumford as a man of science, and his ability as a writer, that his failure to acknowledge the value of the efforts of his predecessors seemed like a tacit condemnation of them, and proved the severest blow to the cause."

"Mr. Culin read a communication from Mr. Charles Laubach, of Riegelsville, Bucks Co., Pa., giving an account of the stove plates manufactured at Durham Furnace, Durham, Pa., from 1741 to 1789."

"Iron stoves were unknown before 1678, when Prince Rupert, of England, attempted to convert a fireplace into a furnace. This was the first attempt to force smoke back over the fire and create heat for warming apartments by the aid of iron."

"[A]bout 1710, Count Polignac, of France, made an attempt to convert an ordinary fireplace into a heating apparatus by simply constructing a fireplace with an iron back, hearth, and jambs. The result was only a slight saving of heat. In 1716 Dr. Desaguliers, of London, succeeded in improving the Polignac fireplace so that it could be used for burning coal."

"The first attempt at manufacturing heating apparatus at Durham, Pa., was in 1741, by the Durham Furnace Company. The firm consisted of George Taylor (later one of the signers of the Declaration of Independence), James Logan and James Morgan, iron masters (the latter being the father of General , the hero of Cowpens)."

"In 1745 Franklin invented the famous stove which bears his name. This pattern continued to be cast at the Durham Furnace until 1774, and probably later."

"The object of the art of heating is to secure this required warmth with the greatest economy and efficiency. ...For reasons of health it may be assumed that no system of heating is advisable which does not provide for a constant renewal of the air in the locality warmed, and on this account there is a difficulty in treating as separate... the subjects of heating and ventilation... The object of all heating apparatus is the transference of heat from the fire to the various parts of the building it is intended to warm, and this transfer may be effected by , by conduction or by . An open fire acts by radiation; it warms the air in a room by first warming the walls, floor, ceiling and articles... and these in turn warm the air. Therefore... the air is... less heated than the walls. In many forms of fireplaces fresh air is brought in and passed around the back and sides of the stove before being admitted into the room."

"The open grate still holds favour... though... it has been superseded by the closed stove. The old form of open fire is... wasteful of fuel, and the loss of heat up the chimney and by conduction into the brickwork backing of the stove is considerable. Great improvements, however, have been effected in the design of open fireplaces, and many ingenious contrivances... are now in the market..."

"Unless suitable fresh air inlets are provided, this form of stove will cause the room to be draughty, the strong current of warm air up the flue drawing cold air in through the crevices in the doors and windows. The best form of open fireplace is the ventilating stove, in which fresh air is passed around the back and sides of the stove before being admitted through convenient openings into the room. This has immense advantages over the ordinary type of fireplace. The illustrations show two forms of ventilating fireplace..."

"The years of the central- fireplace brought the development of the first s. ...Metal andirons in their functional form consisted of two vertical bars on flat or arched leg bases, with an elevated horizonal cross-brace to space them apart and keep them upright. ...The upper part of the vertical members featured extended prongs or notches. This gave support for a horizontal rod, or spit, for cooking meat, and... hanging cooking pots directly over the fire."

"The first wall fireplaces were constructed without chimneys. They used an extended masonry or metal hood over the fire. Smoke exited through a simple hole through the wall... Early fireplaces... had no sides or other devices to form a firebox. ...Many fireplaces of the wall type were located in a corner of a room."

"[C]rude efforts were eventually adopted to create s of s to channel the unwanted smoke... The masonry surface behind the fire aided... radiating heat, and the heavy mass... in the wall and the chimney stored heat... increasing its efficiency."

"Early experiments... led to a method to create firebrick... for... the... firebox. ...s were made more tight with the emergence of fired-clay pipe or flue liners."

"Experiments by, and the design work of... led to the type of fireplace closest to the present day configuration. ...The designs Thompson perfected were known as Count Rumford Fireplaces."

"Many homeowners abandoned the fireplace as a means of cooking with the emergence of the eighteenth century manufactured stoves. Led by the development of... the ', other types of cast iron stoves became available, including the potbelly stove and the massive kitchen range. The advantages offered by the stoves included radiation from the heated cast iron surfaces, better draft for more efficient burning, and successful operable dampers to regulate the fire."

"Our present century has seen the development, manufacture, and widespread use of double-walled steel heat-circulating fireplace unit."

"The desire for safe, efficient fireplace units led designers and engineers to develop the factory-built, so-called zero clearance fireplace unit."

"Fireplaces have... come a long way from their crude "open fire" origins to... safe, efficient units... The heavy masonry materials... are no longer necessary. The amount of space required has been dramatically reduced, and the amount of labor... as well. ...Current fireplaces provide the inherent "charm"... while serving as an efficient and usable source of heat."

"Cooling by evaporation of water or by fans and warming by heaters and fireplaces are artificial aids... From a practical, economic, or aesthetic point of view it makes much more sense to develop, where possible, constructional features for warming or cooling the owner-built home."

"The design of a house around its massive, central fireplace has... always felt right to this writer-builder."

"The fireplace designed and built by the author... is unobstructed, free-standing, and insistent, at the same time that it is supportive of the roof. It is central to the room... as it stands sunken, in its fire pit. ...[W]here the massive stone chimney rises to pierce the roof, a translucent band cascades filtered, mellow illumination [from integrated skylights] down the stone face."

"Unfortunately, most of the technical improvements in fireplace design have not yet emerged into common usage... in spite of the fact that improvements occurred as far back as 1624, when Louis Savot invented the first heat-circulating fireplace. His unit... became the prototype for Ben Franklin's 1742 Pennsylvania stove. The 1624 French fireplace achieved 30 to 45 percent more efficiency than... most American tract-home fireplaces today!"

"Few people are aware that practically all of the technical features of Franklin's... stove were copied from earlier inventors. [Louis] Savot's concept of a preheated draft was employed by Franklin... Prince Rupert's descending flue, invented in 1687, was also applied... The smoke rose in front of a hollow metal back, passing over the top and down the opposite side. ...Ducts similar to those invented by Nicholas Gauger, in 1716, were also incorporated in the Franklin stove."

"The most noteworthy development of the open fireplace took place in 1796, when... Count Rumford published... "Chimney Fireplaces." His main contribution was the alleviation of the smoking chimney. One fault... he... asserted, was due to the large chimney throat. Rumford also introduced the inclined fireback, which increased fireplace effeciency by providing... greater . For the purpose of breaking up the current of smoke in the... downdraft, the back smoke shelf of Rumford's improved fireplace ended abruptly—a practice strictly adhered to... to this day."

"It is more important for the owner-builder to understand the aerodynamics of combustion and ventilation than... detailed specifications for one particular fireplace..."

"[T]he operation of a standard fireplace will effect the displacement of over twice the amount room air required for optimum ventalation. Half the amount... should therefore, be drawn from outside... pass only indirectly through the building, and be prevented from immediate escape through the fireplace."

"Fireplace installation in... efficiently weather-stripped houses creates a problem of... sufficient air for chimney draft. A partial vacuum... is the result, tending to pull smoke and combustion gases... into the room."

"Air-intake control is the key to efficient fireplace combustion. The ignition of a correctly proportioned gas-air mixture will promote... complete combustion... and emit "clean" gases... carbon dioxide, water vapor, oxygen, and nitrogen."

"When smoke and soot are... coming out of a chimney... combustion is incomplete."

"[F]oot-chilling floor draft was... solved by Savot through... a subfloor inlet return for previously heated air. ...[T]his ...would eliminate ...trouble frequently encountered in modern homes ..."

"The owner-builder, desirous of eliminating foot-chilling floor drafts, should... consider... a sunken hearth... and there is less danger of flying sparks..."

"Count Rumford was the first to extensively study inside-fireplace proportions. ...Deep-set fuel beds produce more smoke... since there is scant combustible air at the back... [T]he rate of smoke emission increases proportionally to the depth of the firebox, especially in the early stages of firing."

"Count Rumford's conclusions about the relationship between the chimney throat and effective draft have yet to be scientifically questioned. The throat opening should... constrain the effluent, so that it will be forced to... a speed high enough to discourage down drafts."

"A groundbreaking advance on the way to efficient structures in steel construction was the principle of using tetrahedra as a basic module instead of rectangular geometries. The inventor is considered to be the all-round genius Alexander Graham Bell, who became famous for the invention of the telephone and who built kites that were big enough to lift people into the air. Another engineering genius was Vladimir Grgorevic Suchov, whose genius can definitely be compared to Gustav Eiffel. In 1919 he designed towers up to 350 m high on the principle of hyperbolic paraboloids. The lightness of his constructions is seldom achieved even today, in Moscow there is a television tower with a height of 160 m. His tent constructions with suspended steel grids can be seen as the forerunners of the Olympic roof in Munich or the new Center Pompidou Metz. In , Suchov realized the first double-curved lattice shells on the floor plan of rectangular halls as early as the 19th century. Most of the structures still in existence are massively endangered by corrosion and destruction; current rescue operations are trying to preserve this legacy."

"Shukhov's water tower['s]... double curved surface... was generated by a mesh of straight members overlapping in contrary directions... supported by horizontal rings. While... constructed from steel... Shukhov's 1896 patent application... initially mentions straight wooden beams as a material option. ...[T]he ...application describes ...being able to resist extreme forces while using very little material. As a result, Shukhov's... design was used extensively throughout Russia in the first half of the twentieth century."

"The theory of minimal surfaces and surfaces of constant mean curvature is a vigorously developing branch of mathematics which has a broad range of applications in physics, chemistry and biology where it investigates, for example, soap films and bubbles, bimaterial interfaces or capillaries. Over the past decades, it was also boosted by the anticipated nanotechnology applications. Applications of minimal surfaces have been extensively explored in the sculpture (see e.g. the works by ) and in architecture (s, the Shukhov radio tower ... works by etc.) The first mention of minimal surfaces goes back to Lagrange (1798), who considered the... variational problem..."

"Construction history teaches us that excellent, huge structures like this one are invariably the result of a specific and singular solution, in which all aspects were reflected upon before or after early experiences in the building sequence. The author wants to compare the achievement of Segovia Aqueduct with more recent singular structures: the Oka electricity pylons (1929) by... Vladimir Gregoryevich Shukhov... and the roof of the 1972 Olympic Games in Munich, by a team directed by Gunter Behnish, , /, and Jürgen Linkwitz..."

"The structures of the great Russian engineer Vladimir Grigor'evič Šuchov (Shukhov) are among the world's most sophisticated and distinctive in the history of steel construction. These extremely stable structures, such as cable-stabilised arches, doubly curved grid-shells and above all lattice towers hold a great fascination... They result from the desire to achieve an engineering objective using as little material as possible. ...[T]hey are a testament to the extraordinary creativity and inventiveness of an extensively educated engineer ..."

"Many engineering structures of today were anticipated in Shukhov's works. Some of his others have no modern equivalent or have remained unmatched in their visual impact and... technical efficiency. Among these are... the lattice towers... Countless towers with this new type of construction and geometries defined by just a few parameters were built [by him]... The fine-lined tower structures served as water towers, lighthouses, power transmission masts and fire brigade watchtowers—with some of them still in use today"

"Matthias Beckh analyzes these hyperbolic lattice towers... [and] demonstrates how... Shukhov was already parameterizing his structures as part of the design... Modern methods... provide... Beckh with the tools to place Shukhov's achievements in a historical context and validate their considerable contribution to the history of . He also...demonstrate[s] their relevance to modern structures. ...Beckh was part of the first research project into Shukhov's structures ...The research project ...included in-depth studies of building history ...and detailed investigations into the way the structures were built. Later investigations were intended to provide ...knowledge about the load assumptions... also... relevant to modern structures."

"The object of this book is gain deeper knowledge on the architectural history of hyperbolic structures. The focus of the investigation is the first hyperbolic lattice towers ever built, the work of... Shukhov."

"This form of construction, which had no predecessors... is notable for its strength and economy of materials. Added to this is the high visual impact..."

"Even today, Shukhov's load-bearing system can be found in one form or another in architecture..."

"This book presents the results of the first ever extensive analysis of the way these structures work."

"The of a one-sheeted hyperboloid is resolved into three different mesh variants to create open lattices and their structural behaviour investigated."

"Particular attention is paid to evaluation and analysis of Shukhov's tower calculations and the assumptions made for the structural model. His historical calculations are compared to the results of modern calculations."

"Shukhov's design process is reconstructed and the development of the water towers... illustrated."

"Until now, the form and geometry of the hyperbolic lattice structures have only been investigated to a limited extent."

"A paper by Peter de Vries discussed the stiffness of simple hyperbolic lattice structures and highlighted a single connection between geometry and structural behaviour. The focus... is... on a simple form of hyperbolic lattice structure which always has the intermediate rings positioned at intersection points of the lattice members."

"[T]he form and structure of the Sukhov-built towers were developed not on geometrical or constructional criteria alone, their designs specifically took into account considerations."

"The chapter "Geometry and form of hyperbolic lattice structures"... deals with the form and geometry... A precise description of the mathematical principles of a one-sheeted hyperboloid precedes an explanation of the parametrisation..."

"[T]he chapter "Structural analysis and calculation methods"... considers the principle means of transfer of vertical and horizontal loads and describes the interactions between geometry and structural behaviour. Then... an explanation of the theoretical principles of determining a lattice tower's ultimate load capacity."

"The chapter "Design and analysis of Sukhov's towers"... is devoted to consideration and analysis of Sukhov's structural calculations... Sukhov's design process is reconstructed based on... calculations of five different water towers. From... tables stored in the Moscow city archives, a summary... is produced to chart the development of the towers over more than three decades..."

"An analysis of the design and construction of the NiGRES tower on the Oka... The initial ensemble of four electricity transmission masts represents the consummation of Shukhov's tower construction method. Only one... remains... today."

"The final chapter "Towers in comparison"... contains an extensive table and drawings of 18 towers."

"It is hoped that the examination of Sukhov's form of construction made public in this book will give an impetus to new applications in architecture."

"[A] new reconfigurable doubly-curved structure has been developed for a canopy roof."

"[A] series of kinetic structures which are capable of geometric transformations have been developed. ...[T]he most impressive ones are deployable bar structures with [a] single degree-of-freedom ...These structures ...may become stable and carry loads ...Therefore ...may offer viable solutions for architectural applications, especially for temporary buildings, emergency shelters, exhibition halls, outdoor recreation facilities or sporting fields ...[M]ost of them are composed of scissor like elements (SLEs) ...which is a complex structural system ...[P]resent solutions are insufficient to constitute real form flexibility, because they are limited to... forms such as singly-curved vaults and doubly-curved synclastic s."

"Due to... complexity... doubly-curved anticlastic surfaces such as hyperboloid and hyperbolic paraboloid (HP) have been rarely used for deployable structures. In fact, anticlastic structures can be easily constructed using simple straight bars rather than SLEs since their geometric forms can be generated by s..."

"[A]nticlastic structures are capable of resisting... various design loads through their curvatures and twists. Thus, their structural efficiency is more than ...others. ...[W]e have decided to use HP ...as a [deployable] canopy roof structure."

"In 1829... Nikolai Ivanovich Lobachevsky published a disproof of Euclid's fifth or using the case of a doubly curved surface, thereby establishing non-Euclidean geometry."

"According to Elizabeth C. English, there was a direct connection between the mathematical discoveries of Lobachevsky and the structural explorations of"

"The "idea of the " and the first... diagrid structure have been credited to... Shukhov. The design evolved as an efficient and easily constructed tower for carrying a large gravity load... a water tower. The "Shukhov Tower"... 1896, relies on the use of a diagonal lattice of steel angles, constrained laterally... by steel rings. ...The tower is hollow, requiring little resistance to wind loads ..."

"Shukhov is credited with the construction of some 200 towers using this method ..."

"Although the slender steel sections, when formed into the hyperbolic paraboloid shape, did undergo some bending, a diagrid shape emerges, using a combination of straight segments that are joined at their nodal points of intersection."

"The Shukhov towers tended to use much longer steel sections and overlap them at their crosspoints, rather than using the crosspoints as "nodes" in the fashion of later or spaceframe structures."

"[T]he diagrid form could support both the gravity loads and the lateral loads without requiring additional means. In comparison, the new skyscraper types that were under development at this time used a steel frame to support the gravity loads... while the central core provided the stiffness required to resist wind loads. Where additional resistance was required, it was usually the core that carried the bracing."

"The School of Engineering and Construction which came into being in Russia after the reforms of the 1860s, and in connection with large-scale railway construction towards the end of the nineteenth century, soon acquired a worldwide reputation. It produced distinguished theorists and practitioners who included Belelyubsky, Loleit, Proskuryakov, Shukhov and Yasinsky. The engineering work incorporated in the most diverse kinds of buildings in Russia during the last quarter-century before the Revolution show that this country not only kept pace with the more developed parts of Europe and the USA, but outstripped them in certain fields, in terms of engineering design, as well as the use of modern construction techniques and new materials. Thus Shukhov produced many original designs unparalleled in work done abroad. At the Nizhny-Novgorod Exhibition in 1896... several original designs by Shukhov appeared, the most important of which were latticed: suspended latticed roofs for exhibition halls with a circular, elliptical and rectangular ground plan, latticed roof vaults and hyperbolic latticed towers. This category of structure also included the dual curvature roof designed by Shukhov in 1897-98 to cover the workshop at the Vykhsusnk factory."

"Forms of spanning which have come into use in recent years were foreshadowed in various forms of latticed structures designed by Shukhov before the end of the last century—guyed structures, the spanning of dual curves by structures of standardized rods, the provision of curved 'hyperbolic' profiles by means of a straight component, using straight rods in Shukhov's case."

"Russian engineers made many new and stimulating contributions to the design and construction of multiple-span lattice metal bridges, a great number of which were needed in railway work because of the multitude of large rivers in Russia. Ferro-concrete was first used in buildings there at the beginning of the twentieth century. Russian engineers... made their own contribution to the development of structural techniques in this area."

"The creative principles of innovative trends such as Rationalism and Constructivism were well understood by engineers and constructors bent on applying the latest technological achievements. Great engineers such as Shukhov, [Artur] Loleit and [Hermann] Krasin, were happy to work with innovative architects. They jointly explored new ways of developing architecture, and engineers became active members of Asnova and Osna. ...In the twenties... Soviet architecture set tasks for the building industry which prompted the employment of new materials and structural elements, and raised building standards. Engineering technology in the building industry achieved great successes during this period, such as the metal structures by Shukhov and Krasin, Loleit's work in the field of ferro-concrete, the elaboration of modern timber work by Karlson and the production of new hyperbolic paraboloid roofing by Markarova. The very latest structures and building materials, as well as modern production methods, were applied in the construction of engineering and industrial buildings such as Shukhov's radio tower in Moscow in 1922 and Krasin's viaduct at the Shatura power station in 1925."

"[H]yperbolic s are associated with nuclear and thermal power plants... they are also used... in some large chemical and other industrial plants. [T]hey are high rise structures in the form of doubly curved thin walled shells of complex geometry..."

"The in-plane membrane actions primarily resist the applied forces and plays the secondary role in these special structures."

"The first hyperboloid shaped cooling tower was introduced by the Dutch engineers and Gerard Kuypers and built in 1918 near having 35 meter height."

"The hyperbolic geometry has advantage of a negative which makes it superior in stability against external pressures..."

"The widened bottom of the tower accommodates large installation of fill to facilitate the evaporative cooling of the thin film of circulated water. Narrowing effect of the tower accelerates the of evaporation and diverging top promotes turbulent mixing which increases the contact between hot inside air and cooler outside air."

"The... structure is made of high-strength [cement,] Reinforced... Concrete... in the form of hyperbolic thin shell standing on diagonal, meridional, or vertical supporting columns and radial supports. The shell is sufficiently stiffened by upper and lower edge members."

"[T]o achieve sufficient resistance against instability, large cooling tower shells may be stiffened by additional internal or external rings which may also be used as repair or rehabilitation..."

"The hyperbolic form of thin-walled towers provides optimum conditions for good aerodynamics, strength, and stability."

"[T]he first cooling tower shell [to be] analyzed by means of a shell bending theory [was in 1967]."

"[T]he most preferred method of the modeling and analysis of NDCT [natural draft cooling towers] is [the] (FEM)."

"Determination [utilizing nonlinear static analysis] of the ultimate strength of the cooling towers... subjected to the severe quasistatic wind loads is one of the [research] objectives... for... structural engineers. Various nonlinear factors, such as the material nonlinearities in the concrete and reinforcing steel, tensile cracking, the bond effects between concrete and steel in the cracked concrete which is known as the tension stiffening, the large displacement effects, and so on; need to be taken into account..."

"Mahmoud and Gupta... concluded that the failure of the Port Gibson Tower [in] Mississippi was caused by the circumferential in the vicinity of the throat rather than the yielding of the reinforcement, which contradicts... previous researchers."

"Deformation response and ultimate strength of RC shell structures are governed predominantly by material response of concrete and reinforcing steel, tensile cracking of concrete, [and] bond between concrete and steel.... Softening response of concrete due to quasi-brittle cracking in tension also... influences the nonlinear response by inducing loss of strength and stiffness... Due to all [of] these, analysis requires attention for realistic modeling of the layer of shell concrete confined between the reinforcement layers. ...[O]ne of the most challenging areas... is the modeling techniques using the layered elements."

"The NDCT [natural draft cooling tower] shell structures are submitted to environmental loads such as wind, earthquake and thermal gradients that are in nature. The dead loads, settlement, and construction load are... common... and various accidental loads, e.g., explosion [are]... experience[d]... in their lifetime."

"[I]n 1967, closed-form expressions [were] derived by Gould and Lee... for determining... stresses in the shell and corresponding deformations under static seismic design load."

"Abu-Sitta and Davenport... investigated the effects of dynamic earthquake loading. ...[I]nduced dynamic stresses were related to equivalent membrane stresses from static loads, resulting in... a simplified earthquake analysis procedure."

"Asadzadeh et al... studied the structural response... under static wind and pseudo static seismic forces. ...[T]wo types of... column supports at the base of the towers had been considered... The structural response... under wind and earthquake was... completely different for the towers supported on different columns."

"Asadzadeh et al... studied the effects of the inclination angle of the supporting columns on the dynamic response of the cooling towers. ...[S]tiffness of the structure increases with increase in inclination angle of the supporting columns resulting in decrease of the period therefore altering the resistance... against the earthquake loading. ...[T]he hyperbolic structure... can be optimized by finding the optimum inclination angle of the supporting columns."

"Wind is the prime lateral load and its combination with self weight of the tower shell can cause the instability leading to catastrophic failure."

"After the sudden collapse of three immense cooling towers at Ferry-Bridge Power Station in England in 1965, experimental and theoretical investigations had been done in... the stability of hyperbolic shells to study the parameters increasing the wind resistance and buckling safety..."

"The wind-induced response... is the key factor to improve safety and to reduce tower crack[ing]..."

"Form... found that the construction of the stiffening rings significantly influenced the safety factor (BSF) and structural buckling stability... He showed that adding 2, 3, or 4 stiffening rings to the cooling tower increase the BSF of the R.C. shell by a factor of 1.65, 2.32, and 2.80, respectively."

"Sabouri-Ghomi et al... investigated... buckling stability of R.C. cooling towers supported on X-shaped columns by considering... parameters such as the number, dimension, and location of stiffening rings... The stiffening rings behaved flexibly or rigidly, depending on their dimensions. The number of flexible stiffening rings required to maximize the buckling safety factor was found to be higher than the number of rigid stiffening rings..."

"Ref: S. Sabouri-Ghomi, M.H.K. Kharrazi, and P. Javidan, "Effect of stiffening rings on buckling stability of R.C. hyperbolic cooling towers," Thin Walled Structures, vol. 44, no. 2, pp. 152-158, 2006."

"Zhang et al... studied the effect of the stiffening ring... to improve the dynamic properties and the wind resistance... They... concluded that for the latitude and meridian directions, the stiffness in the latitude direction contributes more... and... the location where the maximum modal displacement of the unstiffened HCT appears will not always be the most effective place for an additional stiffening ring unless the mode shapes of the unstiffened and stiffened HCTs are similar."

"Consideration of the soil–structure interaction... is extremely important when the soil or the foundation medium is not very firm. ...[U]nder ...dynamic loadings, the structure interacts with the surrounding soil imposing soil deformations. These... change the response of the structure."

"Noorzaei et al... analyzed the cooling tower–foundation–soil system under vertical and lateral load generated due to self-weight and wind loads. In this study, the unsymmetrical wind pressure distribution in terms of [were] given..."

"The collapse of three natural draft cooling towers at the Ferry bridge power station in 1965... [was] due to the inadequate design for the wind forces..."

"In recent years... numerical simulation... has been applied to describe the collapse of structures, e.g., the collapse of cooling towers under blasting demolition... and the collapse of the World Trade Center..."

"Due to the complexity of the building procedure, uncertainties in the material properties as well as differences between the theoretical and the real geometry... reliability analysis... seems... indispensible..."

"This review is a complete collection of the studies done for cooling towers and... [gives] updated and sufficient materials for the researches in this field."

"We present a new mechanical model of interatomic bonds, which can be used to describe the elastic properties of the carbon allotropes, such as , diamond, , and s. The interatomic bond is modeled by a hyperboloid–shape structure."

"[T]here are... approaches that are closer to the field of the classical mechanics... so–called structural or discrete-continuous methods... The most straightforward example... is a modeled by the solid deformable rod... [T]he interatomic bonds are modeled as a deformable body or a construction. ...[T]hese approaches... can be implemented in standard computing packages based on the finite–element, boundary–element, or s. These methods can be considered as the bridges between the s of atomistic and continual models of the material."

"In this paper, the carbon bond model is built on the symmetry properties of the hyperboloid. These properties allow it to achieve a high ratio of the lateral and longitudinal , therefore the hyperboloid shapes are widely used in the engineering to create lightweight constructions consisting of straight beams that are known for being able to carry a large load while achieving a low use of raw materials."

"[T]he first hyperboloid tower was built by Russian engineer V.G. Shukhov in (1896)... Being widely demanded in architecture and engineering, such models still haven’t found a wide use in micro- and . It appears that the analogy drawn from the macro level will allow to describe correctly the properties of carbon materials at the micro level."

"Alongside Shukhov’s drawings and sketchpads... a typescript produced by Shukhov’s former employee Grigory Kovelman... put together an extensive overview of Shukhov’s inventions and projects, both as a biographer and as a specialist who had worked with Shukhov.... Elena Shukhova... grand-daughter... presents extensive biographical details in Vladimir Grigorevich Shukhov. The First Engineer in Russia... Art of Construction... is a valuable collection of articles about Shukhov and his various inventions, written by... specialists. It includes... examples of his calculations. Shukhov’s own book Rafters... discusses the mathematical investigations which led him to conceptualise the spatial lattice structure, describing it as 'an optimisation process'."

"In 2010, the journal Detail published an analysis of Shukhov’s constructions, calling his approach to design 'an early example of ’..."

"Vaulted gridshell constructions... were formed with thin metal arches turned away from the frontal position at a particular angle. They thus worked as one continuous resilient truss. ...Each arch was made with rigid metal strips of equal length... during the assembling process, each piece was bent equally. ...It was the first time in the world’s building practice that double-curved spatial vaults were created with single type rod elements ..."

"Shukhov’s lattice-suspended and vaulted structures represented a carrying surface, which could be shaped in any form. ...The density of the grid made it possible to attach it to the shell without additional structures. ...[T]he grids were two to three times lighter than roofs with conventional frames..."

"The final and most unusual of the gridshell structures presented at the Exhibition was the 32-metre-tall lattice hyperboloid water tower. Everything was amazing in that first Shukhov tower—everything in it was some structural and geometric puzzle: straight rods and the external silhouette double curvature, the openwork lightness below and the solid heaviness above."

"The water tower was a unique structure of its time... According to Cooper, the idea... came directly from an imaginary hyperboloid geometry, invented by... Lobachevski in 1829..."

"Grigory Kovelman writes that Shukhov told him he had been thinking about the properties of hyperboloid structures for a long time, that he had studied hyperboloid forms at the Technical School, and that apparently the moment of enlightenment came about when he saw an up-ended wicker wastepaper basket with a focus on top of his desk. According to Shukhov, this was when he understood clearly how a hyperboloid structure with its curved surface [was] generated by straight rods..."

"[T]he structure of the lattice tower was a spatial system, where the load was equally spread along the surface. ...Aiming to optimise the design process, soon after building the tower Shukhov presented the standardised elements of the tower structure in a table format... with the aid of which it became possible to design a new water tower according to a client’s requirements in twenty-five minutes..."

"The Radio Tower in Moscow is a gridshell which aims for structural efficiency. Its minimal surface and open lattice structure help in reducing the wind load, one of the main challenges in high-rise building design. ...Shukhov's design logic focuses on structural . The rings between the different segments offer additional reinforcement to create an equilibrium between minimal material consumption, structural efficiency and geometry."

"As hyperboloid structures are double curved, that is simultaneously curved in opposite directions, they are very resistant to . This means that you can get away with far less material than you would otherwise need..."

"Single curved surfaces, for example cylinders, have strengths but also weaknesses. Double curved surfaces... are curved in two directions and thus avoid... weak directions."

"[T]his is the magical part... despite the surface being curved in two directions, it is made entirely of straight lines. Apart from the cost savings of avoiding curved beams or shuttering, they are far more resistant to buckling because the individual elements are straight..."

"This is an interesting paradox: you get the best local buckling resistance because the beams are straight and the best overall buckling resistance because the surface is double curved."

"The hyperboloid is the design standard for all nuclear cooling towers and some coal-fired power plants."

"When designing... cooling towers, engineers are faced with two problems: I. The structure must be able to withstand high winds and II. They should be built with as little material as possible... The hyperbolic form solves both..."

"For a given diameter and height of a tower and a given strength, this shape requires less material than any other form. ...Hyperboloidal towers can be built from or as a steel lattice, and is the most economical such structure for a given diameter and height."

"The presented orthogonal fitting algorithm can be applied easily for ellipsoid, and sphere also other surface[s] such as paraboloid."

"In 1899... V. Shukhov... patented the principle of constructing hyperboloid gridshell structures based on a hyperboloid of revolution. ...A one-sheet hyperboloid is a connected surface having negative at each point. Through any point of this surface, two intersecting [straight] lines can be drawn, completely belonging to it. Thus the... surface can be formed by the set of straight lines. It the steel beams would be placed along these lines the shape... could be retained under... external loading... [I]n Shukhov's towers horizontal rims [rings] were used... located at different levels... The stability... was ensured by numerous riveted connections... During the installation... the straight angles of the metal profile was somewhat deformed... [at] the... intersecting elements in order to ensure maximum contact... by rivets."

"The main hazard for high-rise structures is the loads caused by wind gusts. The grid shell design... minimize[d] their influence. Open-work design... ensured... sufficient strength, high stability and low metal consumption. ...[C]onsumption of metal per unit height... was three times less than... the ..."

"... Ještěd in Czechia, Guangzhou in China... and Khan Shatir Shopping-Entertaining Center in Kazakhstan, Aspire Tower in Qatar... are vivid examples of using... the hyperboloid principle... [in] modern buildings."

"191 of the Shukhov's Towers (from known near 200...) have been irretrievably lost during... the 20th century... [Some] towers were destroyed because their continued use for water supply has become impractical. To use them for another purpose... large investments were necessary."

"The extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains."

"... the Roman prudence was more particularly employed on matters which had received but little attention from the Greeks, such as paving their roads, constructing aqueducts, and sewers, to convey the sewage of the city into the Tiber. In fact, they have paved the roads, cut through hills, and filled up valleys, so that the merchandise may be conveyed by carriage from the ports. The sewers, arched over with hewn stones, are large enough in some parts for waggons loaded with hay to pass through; while so plentiful is the supply of water from the aqueducts, that rivers may be said to flow through the city and the sewers, and almost every house is furnished with water-pipes and copious fountains."

"But let us now turn our attention to some marvels that, if justly appreciated, may be pronounced to remain unsurpassed... If we take into account the abundant supply of water to the public, for baths, ponds, canals, household purposes, gardens, places in the suburbs and country houses, and then reflect upon the distances that are traversed from the sources on the hills, the arches that have been constructed, the mountains pierced, the valleys leveled, we must perforce admit that there is nothing more worthy of our admiration throughout the whole universe."

"Aqueducts were a combination of beauty and stability, quintessentially Roman, being practical and monumental at the same time."

"And in the midst of all, a fountaine stood, Of richest substaunce, that on earth might bee, So pure and shiny, that the siluer flood Through euery channell running one might see; Most goodly it with curious imageree Was ouer-wrought, and shapes of naked boyes, Of which some seemd with liuely iollitee, To fly about, playing their wanton toyes, Whilest others did them selues embay in liquid ioyes.And ouer all, of purest gold was spred, A trayle of yuie in his natiue hew: For the rich mettall was so coloured, That wight, who did not well auis’d it vew, Would surely deeme it to be yuie trew: Low his lasciuious armes adown did creepe, That themselues dipping in the siluer dew, Their fleecy flowres they tenderly did steepe, Which drops of Christall seemd for wantones to weepe.Infinit streames continually did well Out of this fountaine, sweet and faire to see, The which into an ample lauer fell, And shortly grew to so great quantitie, That like a little lake it seemd to bee; Whose depth exceeded not three cubits hight, That through the waues one might the bottom see, All pau’d beneath with Iaspar shining bright, That seemd the fountaine in that sea did sayle vpright.And all the margent round about was set, With shady Laurell trees, thence to defend The sunny beames, which on the billowes bet, And those which therein bathed, mote offend. As Guyon hapned by the same to wend, Two naked Damzelles he therein espyde, Which therein bathing, seemed to contend, And wrestle wantonly, ne car’d to hyde, Their dainty parts from vew of any, which them eyde."

"REST! This little Fountain runs Thus for aye:—It never stays For the look of summer suns, Nor the cold of winter days Whosoe’er shall wander near, When the Syrian heat is worst, Let him hither come, nor fear Lest he may not slake his thirst: He will find this little river Running still, as bright as ever. Let him drink, and onward hie, Bearing but in thought that I, EROTAS, bade the Naiad fall, And thank the great god Pan for all!"

"From Evereven’s lofty hills where softly silver fountains fall his wings him bore, a wandering light, beyond the mighty Mountain Wall."

"There are some parts of the world that, once visited, get into your heart and won’t go. For me, India is such a place. When I first visited, I was stunned by the richness of the land, by its lush beauty and exotic architecture, by its ability to overload the senses with the pure, concentrated intensity of its colors, smells, tastes, and sounds. It was as if all my life I had been seeing the world in black and white and, when brought face-to-face with India, experienced everything re-rendered in brilliant technicolor."

"To judge of the past from the present, let us take the English nation in India. It has held India for a longer period than the Greeks did Bactria from the time of Alexander to that of As'oka, but yet it has produced no appreciable effect on the architecture of its neighbours. The Bhutanese and the Sikimites have not yet borrowed a single English moulding. The Nepalese, under the administration of Sir Jung Bahadur, are not a whit behind-hand of As ́oka and his people; Sir Jung went to Europe, which As'oka never did; still there is no change perceptible in Nepalese architecture indicative of a European amalgamation. The Kashmiris and the Afghans have proved equally conservative, and so have the Burmese. But to turn from their neighbours to the people of Hindustan : these have had intimate intercourse with Europeans now for over three hundred years, and enjoyed the blessings of English rule for over a century, and yet they have not produced a single temple built in the Saxon, or any other European style. Thus the conclusion we are called upon to accept is that what has not been accomplished by the intimate intercourse of three centuries, and the absolute sovereignty of a century, in these days of railways, and electric telegraphs, and mass education, was effected by the Greeks two thousand years ago simply by living as distant neighbours for eighty years or so."

"The greatness of this people was attested by "the gigantic grandeur and durability of Egyptian and Indian architecture in contradistinction to the fragile littleness of modem buildings. This consideration will enable us," he continued, "by analogy to grasp the idea . . . that all these famous nations sprang from one stock, and that their colonies were all one people directly or indirectly, of Indian origin.... ""

"From around 1600 to 1750, the Baroque period witnessed the creation of some of the greatest musical masterpieces ever composed."