Nicolas Léonard Sadi Carnot

"Life is a short enough passage. I am half the journey. I will complete the remainder as I can."

"Hope being the greatest of all blessings, it is necessary, in order to be happy, to sacrifice the present to the future."

"Let us not be exacting; perfection is so rare. Indulgence! Indulgence!"

"The more nearly an object approaches perfection, the more we notice its slightest defects."

"To neglect the opportunity of an innocent pleasure is a loss to ourselves."

"Recherché pleasures cause simple pleasures to lose all their attractions."

"It may sometimes be necessary to yield the right, but how is one to recover it when wanted?"

"Love is almost the only passion that the good man may avow. It is the only one which accords with delicacy."

"Do nothing that all the world may not know."

"The truly wise man is he who loves virtue for its own sake."

"We say that man is an egotist, and nevertheless his sweetest pleasures come to him through others. He only tastes them on condition of sharing them."

"If one could continually satisfy his desires, he would never have time to desire. Happiness then is necessarily composed of alternatives. It could not exist at a constant level."

"To each conqueror can be said, when he has ceased tormenting our poor globe, "Would you not have been able to tilt equally well against a little globe of pasteboard?""

"The laws of war, do they say? As if war were not the destruction of all laws."

"War has been represented as necessary to prevent the too rapid increase of the population, but war mows down the flower of the young men, while it spares the men disgraced by nature. Hence it tends to the degeneration of the species."

"The decadence of the Greeks and Romans... proves the influence of institutions upon customs."

"According to the system of modern economists, it would be desirable that the government should interfere as little as possible in the commerce and industry of the country. Nevertheless we cannot deny that in certain circumstances this intervention is very useful."

"Taxes are regarded by economists as an evil, but as a necessary evil, since they provide for public expenses. Consequently, economists think that if the government possessed sufficient revenues, in domains for example, the suppression of all taxes would be a desirable measure."

"Taxes are a means of influencing production and commerce to give to them a direction which they would not naturally have taken. Such an influence may undoubtedly have disagreeable consequences if the taxes are imposed without discrimination or exclusively for a fiscal purpose, but it is entirely otherwise if wisdom and tact preside at their institution."

"Men attribute to chance those events of the causes of which they are ignorant. If they succeed in divining these causes, chance disappears. To say that a thing has happened by chance, is to say that we have not been able to foresee it. I do not myself believe that any other acceptation can be given to this word. What to an ignorant man is chance, cannot be chance to one better instructed."

"If human reason is incapable of discovering the mysteries of Divinity, why has not Divinity made human reason more clear-sighted?"

"God cannot punish man for not believing when he could so easily have enlightened and convinced him."

"If God is absolutely good, why should He punish the sinner for all eternity, since He does not lead him to good, or give him an example?"

"According to the doctrine of the church, God resembles a proposing enigmas, and devouring those who cannot guess them."

"The church attributes to God all human passions—anger, desire for vengeance, curiosity, tyranny, partiality, idleness."

"If Christianity were pruned of all which is not Christ, this religion would be the simplest in the world."

"What motives have influenced the writers who have rejected all religious systems? Is it the conviction that the ideas which they oppose are all injurious to society? Have they not rather included in the same proscription religion and the abuse of it?"

"The belief in an all-powerful Being, who loves us and watches over us, gives to the mind great strength to endure misfortune."

"A religion suited to the soul and preached by men worthy of respect would exercise the most salutary influence upon society and customs."

"[C]hanges caused in the temperature of bodies by motion have been very little studied. This class of phenomena merits... attention... When bodies are in motion, especially when that motion disappears, or when it produces motive power, remarkable changes take place in the distribution of heat, and perhaps in its quantity."

"The Collision of Bodies. ...[I]n the collision of bodies there is always expenditure of motive power. Perfectly elastic bodies only form an exception, and none such are found in nature."

"[A]lways in the collision of bodies there occurs... an elevation of temperature. We cannot, as did M. Berthollet, attribute the heat set free in this case to the reduction of the volume of the body..."

"It would seem... that heat set free should be attributed to the friction of the molecules of the metal, which change place relatively to each other, that is, the heat is set free just where the moving force is expended. ...We may also cite... the heat produced by the extension of a metallic rod just before it breaks... the greater the elongation before rupture, the more considerable is the elevation of temperature."

"When a hypothesis no longer suffices to explain phenomena, it should be abandoned. This is the case with... caloric as matter, as a subtile fluid. The experimental facts tending to destroy this theory are as follows: (1) The development of heat by percussion or the friction of bodies (experiments of Rumford, friction of wheels on... axles...). Here the elevation of temperature takes place at the same time in the body rubbing and the body rubbed. ...Thus heat is produced by motion. If... [caloric] is matter... matter is created by motion. (2) ...[A]ir compressed by the pumps must rise in temperature above the air outside, and it is expelled at a higher temperature. ...Thus heat has been created by motion."

"[[Light|[L]ight]] is generally regarded as the result of a vibratory movement of the ethereal fluid. Light produces heat, or at least accompanies the radiating heat, and moves with the same velocity as heat. Radiating heat is then a vibratory movement. It would be ridiculous to suppose that it is an emission of matter while the light which accompanies it could be only a movement."

"Could a motion (that of radiating heat) produce matter (caloric)? No, undoubtedly; it can only produce a motion. Heat is then the result of a motion. Then it is plain that it could be produced by the consumption of motive power, and that it could produce this power."

"Is heat the result of a vibratory motion of molecules? If... so, quantity of heat is simply quantity of motive power. As long as motive power is employed to produce vibratory movements, the quantity of heat must be unchangeable... but when it passes into movements of sensible extent, the quantity of heat can no longer remain constant."

"Liquuefaction of bodies, solidification of liquids, crystallization—are they not forms of combinations of integrant molecules?"

"[T]here cannot be loss of living force, or, which is the same thing, of motive power, if the bodies act upon each other without directly touching each other, without actual collision. ...[T]he molecules of bodies are always separated from each other by some space ...they are never actually in contact. If they touched each other, they would remain united, and consequently change form. If the molecules of bodies are never in close contact with each other, whatever... forces... separate or attract them, there can never be either production or loss of motive power... This power must be as unchangeable in quantity as matter."

"Heat is simply motive power, or rather motion which has changed form. It is a movement among the particles of bodies. Wherever there is destruction of motive power there is, at the same time, production of heat in quantity exactly proportional to the quantity of motive power destroyed. Reciprocally, wherever there is destruction of heat, there is production of motive power."

"[[Energy|[M]otive power]] is, in quantity, invariable in nature; that it is, correctly speaking, never either produced or destroyed. It is true that it changes form, that is, it produces sometimes one sort of motion, sometimes another, but it is never annihilated."

"Carnot's work, Sur la Puissance Motrice du Feu, is the first in which any attempt is made to explain the production of work from heat. It is unfortunately marred by his assumption, that heat is a material substance, though it is only fair to say that he expresses grave doubts as to the truth of this hypothesis. ...He begins his investigation by premising the following correct principle, sadly neglected by many subsequent writers: 'If a body, after having experienced a certain number of transformations, be brought identically to its primitive state as to density, temperature, and molecular constitution, it must contain the same quantity of heat as that which it initially possessed.' Hence he concludes, that when heat produces work, it is in consequence of its being let down from a hot body to a cold one, as from the boiler to the condenser of a steam-engine. His investigation... forms the foundation of the modern theory."

"In the nineteenth century Sadi Carnot combined the old idea that perpetual-motion machines are impossible (an early and incomplete version of the first law) with the (heat is a substance) to prove that in a heat engine a discharge of heat to the cold surroundings was inevitable. From this starting point, he and others deduced some remarkable conclusions about the efficiency of heat engines and about the properties of matter..."

"Carnot considered that the steam engine was analogous to another prime mover, the water wheel. The analogy, and the upon which it was based, led Carnot to the incorrect conclusion that no heat was lost, or converted into mechanical energy during the operation of the steam engine. He thought that the same quantity of heat was given out by the boiler at the higher temperature as was received by the condenser at the lower temperature. However, the analogy led him also to the fruitful conception that the amount of energy produced... was solely dependent, in principle, upon the temperature difference between the boiler and the condenser and the amount of heat which passed from the one to the other. Thus it appeared that all heat engines in general, would have the same efficiency if they worked within the same temperature levels. He substantiated this... Carnot's principle, by pointing out that would be possible if it were not true. If two perfect heat engines operating between the same temperature levels did not have the same efficiency, it would be possible for the more efficient... to drive the less efficient engine backwards, pumping heat from the lower to the higher temperature, thus leaving the thermal conditions unchanged and yet generating a continuous excess of energy."

"Later, in 1830, Carnot appreciated that his comparison of... the waterwheel was not exact, and that some heat was converted into mechanical energy... Thereupon he abandoned the and adopted the view that heat was... motions of the particles of bodies, heat and mechanical energy being interconvertible... Carnot died... 1832, and his later views... were not published until 1878."

"Nicolas-Leonard-Sadi Carnot was, perhaps, the greatest genius, in the department of physical science at least, that this century has produced. ...his one little volume, which has made him immortal, was written when he was but twenty-three or twenty-four."

"One could... safely declare that 'Physics... can be defined as that subject which treats of the transformation of energy.' The philosophical version of Herakleitos and Empedokles... a continual cycle of changes and exchanges, had... crystallized into a quantitative physical theory. But this... picture... was... incomplete. For... there was a second, equally general and fundamental element in Nature—a directional one. This had first been formulated in the 1820s by the Mozart of modern physics, Sadi Carnot. ...Carnot started with the question: What proportion of the heat in any system is 'available' as a means of producing mechanical energy? ...Carnot demonstrated ...a one-hundred-per-cent-efficient engine could exploit only a fraction of the heat supplied to it... A 'super-efficient' machine which could exploit all the heat supplied, would be (as Carnot's mathematics proved) a machine... one could get out of it more energy than was supplied... In an ... physical changes could at most be perfectly reversible; [but] in normal cases they would result in the progressive... 'degradation' of mechanical energy by the production of unavailable heat. To characterize this... Clausius coined the word ... [T]he directional principle of Carnot and Clausias (which gave precise expression to Newton's insight that 'motion is more easily lost than got, and is continually upon the decrease') became the Second Law of Thermodynamics."

"On January 16, 1793, the in Paris sentenced to death. Among those who took the fatal decision was... Lazare Carnot... [who] had a passion for the great Persian poet Saadi Shirazi... Carnot names his first son after Saadi. Sadi Carnot is thus born out of poetry and rebellion. As a young man, he develops a passion for those steam engines... beginning to transform the world... In 1824, he writes... "," in which he seeks to understand the theoretical basis of... these machines. The little treatise is packed with mistaken assumptions: he imagines that heat is a concrete entity... fluid that produces energy by "falling" from hot things to cold, just as... a waterfall... But it contains a key idea: that steam engines function... because the heat passes from hot to cold."

"Science and technology are inseparable, in two senses. First, because and understanding of the laws of the universe is always implicit in technology. (Francis Bacon said, "Nature to be commanded must be obeyed.") Second, because, beyond a certain level in technology, the understanding tends to become explicit. Arguably the most profound scientific truth is the second law of thermodynamics, which notes the inexorability of universal chaos and thus... defines the current against which organic evolution and cultural evolution both swim. The earliest statement of the second law came in the nineteenth century from the Frenchman Sadi Carnot, who described himself as a "constructor of steam engines," the vocation that indeed had led him to see the gist of the second law."

"The whole theory rests on a principle generally admitted as an axiom, which Carnot expresses in the following terms:— "In our demonstration, we tacitly assume that after a body has experienced a certain number of transformations, if it be brought identically to its primitive physical state as to density, temperature, and molecular constitution, it must contain the same quantity of heat as that which it initially possessed; or, in other words, we suppose that the quantities of heat lost by the body under one set of operations, are precisely compensated by those which are absorbed in the others. This fact has never been doubted; it has at first been admitted without reflection, and afterwards verified in many cases by calorimetrical experiments. To deny it would be to overturn the whole theory of heat, of which it is a fundamental principle. It must be admitted, however, that the chief foundations on which the theory of heat rests would require a most attentive examination. Several experimental facts appear nearly inexplicable in the actual state of this theory." Since the time when Carnot thus expressed himself, the necessity of a most careful examination of the entire experimental basis of the theory of heat has become more and more urgent. Especially all those assumptions depending on the idea that heat is a substance invariable in quantity, not convertible into any other element, and incapable of being generated by any physical agency..."