Mathematicians From England

"Barrow was familiar with the paraboliforms, and s and areas connected with them, in from 1655 to 1660 at the very latest; hence he could... differentiate and integrate by his own method any rational positive power of a variable, and thus also a sum of such powers."

"He further developed... [infinitesimal calculus] in the years 1662-3-4, and in the latter year probably had it fairly complete. In this year he communicated to Newton the great secret of his geometrical constructions... and it was probably this that set Newton to... attempt to express everything as a sum of powers of the variable."

"During the next year Newton began to "reflect on his method of fluxions," and actually did produce his Analysis per Æquationes. This, though composed in 1666, was not published until 1711."

"Leibniz bought a copy of Barrow’s work in 1673, and was able "to communicate a candid account of his calculus to Newton" in 1677. In... the face of Leibniz’ persistent denial that he received any assistance whatever from Barrow’s book... bear... in mind Leibniz’ twofold idea of the "calculus":— (i) the freeing of the matter from geometry, (ii) the adoption of a convenient notation. ...[O]n these two points ...he derived not the slightest assistance from Barrow’s work; for the first ...would be dead against Barrow’s practice and instinct, and of the second Barrow had no knowledge whatever. ...[F]or [these points] ...the world has to thank Leibniz; but their inception does not mean the invention of the infinitesimal calculus. This, the epitome of the work of his predecessors, and its completion by his own discoveries until it formed a perfected method of dealing with the problems of tangents and areas for any curve in general, i.e. ...the differentiation and integration of any function whatever (such as were known in Barrow’s time), must be ascribed to Barrow."

"My attention was arrested by a theorem in which Barrow... rectified the cycloid, which... has usually been ascribed to Sir C. Wren. ...What I found induced me to treat a number of the theorems ...I came to the conclusion that Barrow had got the calculus; but I queried even then whether Barrow himself recognized the fact."

"Only on completing my annotation of the last chapter of this volume, Lect. XII, App. III, did I come to the conclusion that is given as the opening sentence of this Preface; for I then found that a batch of theorems.., on careful revision, turned out to be the few missing standard forms, necessary for completing the set for integration; and that one of his problems was a practical rule for finding the area under any curve, such as would not yield to the theoretical rules he had given, under the guise of an "inverse-tangent" problem."

"[T]he conclusion is the effect of a gradual accumulation of evidence... I have given a wholly inadequate account of the work of Barrow’s immediate predecessors; but... to a sufficiency for... showing... the time was... ripe for the work of Barrow, Newton, and Leibniz."

"I have to all intents rewritten Barrow’s book; although throughout I... adhered... to Barrows own words. I have only retained those parts which seemed... essential for the purpose in hand. This was necessary... that room might be found for... critical notes on the theorems.., proofs omitted by Barrow, which when given in Barrow’s style, and afterwards translated into analysis, had an important bearing on the point as to how he found out the more difficult of his constructions; and lastly for deductions therefrom that point steadily, one after the other, to the fact that Barrow was writing a calculus and knew that he was inventing a great thing."

"I have used three distinct kinds of type: the most widely spaced type has been used for Barrow’s own words; only very occasionally have I inserted anything of my own in this, and then it will be found enclosed in heavy square brackets, that the reader will have no chance of confusing my explanations with the text... Barrow makes use of parentheses very frequently, so that the reader must understand that only remarks in heavy square brackets are mine... The small type is used for footnotes only. In the notes I... use the Leibniz notation, because it will... convey my meaning better; but there was really no absolute necessity for this, Barrow’s a and e, or its modern equivalent, h and k, would have done quite as well."

"The beginnings of the Infinitesimal Calculus... arose from determinations of areas and volumes, and the finding of tangents to plane curves. The ancients attacked the problems in a strictly geometrical manner, making use of the "s." ... This was the method by means of which Archimedes proved most of his discoveries. But there seems to have been some distrust of the method, for we find... many... discoveries... proved by a '..."

"Galileo... would appear to have led the way, by the introduction of the theory of composition of motions into mechanics; he also was one of the first to use infinitesimals in geometry, and from... what is equivalent to "virtual velocities" it is... inferred that the idea of time as the independent variable is due to him. Kepler... was the first to introduce... infinity into geometry and to note that the increment of a variable was evanescent for values of the variable in the immediate neighbourhood of a maximum or minimum; in 1613, an abundant vintage drew his attention to the defective methods in use for estimating the cubical contents of vessels, and his essay on the subject (Nova Stereometria Doliorum) entitles him to rank amongst those who made the discovery of the infinitesimal calculus possible."

"In 1635 Cavalieri published a theory of "indivisibles," in which he considered a line as made up of an infinite number of points, a superficies as composed of a succession of lines, and a solid as a succession of superficies, thus laying the foundation for the "aggregations" of Barrow. Roberval seems... first, or... an independent, inventor of the method; but he lost credit... because he did not publish it, preferring to keep the method... for his own use... a usual thing... of that time, due perhaps to... professional jealousy. The method was severely criticized... especially by Guldin, but Pascal... showed that the method of indivisibles was as rigorous as... exhaustions... they were practically identical. ...[T]he progress... is much indebted to this defence by Pascal. Since this method is... analogous to... integration, Cavalieri and Roberval have... claim... as... inventors of... one branch of the calculus; if it were not for the fact that they only applied it to special cases, and seem... unable to generalize... owing to cumbrous algebraical notation, or to have failed to perceive the inner meaning... concealed under a geometrical form. Pascal... applied the method with great success, but also to special cases only; such as his work on the ."

"The next step was... more analytical... [B]y the method of indivisibles, Wallis... reduced... many areas and volumes to... the series (0^m + 1^m + 2^m +... n^m) / (n + 1)n^m, i.e. the ratio of the mean of all the terms to the last term, for integral values of n; and later he extended his method, by a theory of , to fractional values of n. Thus the idea of the Integral Calculus was in a fairly advanced stage in the days immediately antecedent to Barrow."

"What Cavalieri and Roberval did for the integral calculus, Descartes... accomplished for the differential branch by his... application of algebra to geometry. Cartesian coordinates made possible the extension of... drawing... tangents to... curves of any kind. ...[H]e habitually used the index notation ...this had a very great deal to do with ...Newton's discovery of the general binomial expansion and of many other infinite series. Descartes failed, however, to make... great progress... in... drawing of s, owing to... an unfortunate choice of a definition for a tangent to a curve in general. Euclid's circle-tangent definition being more or less hopeless in the general case, Descartes had the choice of three:—"

"Fermat... adopted Kepler's notion of the increment of the variable becoming evanescent near a maximum or minimum value, and upon it based his method of drawing tangents. Fermat's method of finding the maximum or minimum... involved the differentiation of any explicit algebraic function, in the form that appears in any beginner's text book of today (though Fermat does not seem to have the "function" idea); that is, the maximum or minimum values of f(x) are the roots of f'(x) = 0, where f'(x) is the limiting value of [f(x+h) - f(x)]/h; only Fermat uses the letter e or E instead of h."

"Here then we have all the essentials for the calculus; but only for explicit integral algebraic functions, needing the binomial expansion of Newton, or a general method of rationalization which did not impose too great algebraic difficulties, for their further development; also, on the authority of Poisson, Fermat is placed out of court, in that he also only applied his method to certain special cases. Following the lead of Roberval, Newton subsequently used the third definition of a tangent, and the idea of time as the independent variable, although this was only to insure that one at least of his working variables should increase uniformly. This uniform increase of the independent variable would seem to have been usual for mathematicians of the period and to have persisted for some time; for later we find with Leibniz and the Bernoullis that d(dy/dx) = (d2y/dx2)dx. Barrow also used time as the independent variable in order that, like Newton, he might insure that one of his variables, a moving point or line or superficies, should proceed uniformly; ...Barrow... chose his own definition of a tangent, the second of those given above; and to this choice is due in great measure his advance over his predecessors. For his areas and volumes he followed the idea of Cavalieri and Roberval."

"Thus we see that in the time of Barrow, Newton, and Leibniz the ground had been surveyed, and in many directions levelled; all the material was at hand, and it only wanted the master mind to "finish the job." This was possible in two directions, by geometry or by analysis; each method wanted a master mind of a totally different type, and the men were forthcoming. For geometry, Barrow; for analysis, Newton, and Leibniz with his inspiration in the matter of the application of the simple and convenient notation of his calculus of s to s and to geometry. With all due honour to these three mathematical giants, however, I venture to assert that their discoveries would have been well-nigh impossible... if they had lived a hundred years earlier; with the possible exception of Barrow, who, being a geometer, was more dependent on the ancients and less on the moderns of his time than were the two analysts, they would have been sadly hampered but for the preliminary work of Descartes and the others I have mentioned (and some I have not—such as Oughtred), but especially Descartes."

"In other branches of science, where quick publication seems to be so much desired, there may possibly be some excuse for giving to the world slovenly or ill-digested work, but there is no such excuse in mathematics. The form ought to be as 102 perfect as the substance, and the demonstrations as rigorous as those of Euclid. The mathematician has to deal with the most exact facts of Nature, and he should spare no effort to render his interpretation worthy of his subject, and to give to his work its highest degree of perfection. “Pauca sed matura” was Gauss’s motto."

"The mathematician requires tact and good taste at every step of his work, and he has to learn to trust to his own instinct to distinguish between what is really worthy of his efforts and what is not; he must take care not to be the slave of his symbols, but always to have before his mind the realities which they merely serve to express. For these and other reasons it seems to me of the highest importance that a mathematician should be trained in no narrow school; a wide course of reading in the first few years of his mathematical study cannot fail to influence for good the character of the whole of his subsequent work"

"Quite distinct from the theoretical question of the manner in which mathematics will rescue itself from the perils to which it is exposed by its own prolific nature is the practical problem of finding means of rendering available for the student the results which have been already accumulated, and making it possible for the learner to obtain some idea of the present state of the various departments of mathematics.... The great mass of mathematical literature will be always contained in Journals and Transactions, but there is no reason why it should not be rendered far more useful and accessible than at present by means of treatises or higher text-books. The whole science suffers from want of avenues of approach, and many beautiful branches of mathematics are regarded as difficult and technical merely because they are not easily accessible.... I feel very strongly that any introduction to a new subject written by a competent person confers a real benefit on the whole science. The number of excellent text-books of an elementary kind that are published in this country makes it all the more to be regretted that we have so few that are intended for the advanced student. As an example of the higher kind of text-book, the want of which is so badly felt in many subjects, I may mention the second part of Prof. Chrystal’s “Algebra” published last year, which in a small compass gives a great mass of valuable and fundamental knowledge that has hitherto been beyond the reach of an ordinary student, though in reality lying so close at hand. I may add that in any treatise or higher text-book it is always desirable that references to the original memoirs should be given, and, if possible, short historic notices also. I am sure that no subject loses more than mathematics by any attempt to dissociate it from its history."

"It would seem at first sight as if the rapid expansion of the region of mathematics must be a source of danger to its future progress. Not only does the area widen but the subjects of study increase rapidly in number, and the work of the mathematician tends to become more and more specialized. It is, of course, merely a brilliant exaggeration to say that no mathematician is able to understand the work of any other mathematician, but it is certainly true that it is daily becoming more and more difficult for a mathematician to keep himself acquainted, even in a general way, with the progress of any of the branches of mathematics except those which form the field of his own labours. I believe, however, that the increasing extent of the territory of mathematics will always be counteracted by increased facilities in the means of communication. Additional knowledge opens to us new principles and methods which may conduct us with the greatest ease to results which previously were most difficult of access; and improvements in notation may exercise the most powerful effects both in the simplification and accessibility of a subject. It rests with the worker in mathematics not only to explore new truths, but to devise the language by which they may be discovered and expressed; and the genius of a great mathematician displays itself no less in the notation he invents for deciphering his subject than in the results attained.... I have great faith in the power of well-chosen notation to simplify complicated theories and to bring remote ones near and I think it is safe to predict that the increased knowledge of principles and the resulting improvements in the symbolic language of mathematics will always enable us to grapple satisfactorily with the difficulties arising from the mere extent of the subject"

"The invention of logarithms and the calculation of the earlier tables form a very striking episode in the history of exact science, and, with the exception of the Principia of Newton, there is no mathematical work published in the country which has produced such important consequences, or to which so much interest attaches as to Napier’s Descriptio."

"Bertrand, Darboux, and Glaisher have compared Cayley to Euler, alike for his range, his analytical power, and, not least, for his prolific production of new views and fertile theories. There is hardly a subject in the whole of pure mathematics at which he has not worked."

"Many of the greatest masters of the mathematical sciences were first attracted to mathematical inquiry by problems relating to numbers, and no one can glance at the periodicals of the present day which contain questions for solution without noticing how singular a charm such problems still continue to exert. The interest in numbers seems implanted in the human mind, and it is a pity that it should not have freer scope in this country. The methods of the theory of numbers 271 are peculiar to itself, and are not readily acquired by a student whose mind has for years been familiarized with the very different treatment which is appropriate to the theory of continuous magnitude; it is therefore extremely desirable that some portion of the theory should be included in the ordinary course of mathematical instruction at our University. From the moment that Gauss, in his wonderful treatise of 1801, laid down the true lines of the theory, it entered upon a new day, and no one is likely to be able to do useful work in any part of the subject who is unacquainted with the principles and conceptions with which he endowed it."

"As in Mathematics in general, the really great advances, embodying new ideas of far-reaching fruitfullness, have been due to an exceedingly small number of great men... there are periods when for a long series of centuries no advance was made; when the results obtained in a more enlightened age have been forgotten. We observe the times of revival, when the older learning has been rediscovered, and when the results of the progress made in distinct countries have been made available as the starting points of new efforts and a fresh period of activity."

"A new point is determined in Euclidean Geometry exclusively in one of the three following ways: Having given four points A, B, C, D, not all incident on the same straight line, then (1) Whenever a point P exists which is incident both on (A,B) and on (C,D), that point is regarded as determinate. (2) Whenever a point P exists which is incident both on the straight line (A,B) and on the circle C(D), that point is regarded as determinate. (3) Whenever a point P exists which is incident on both the circles A(B), C(D), that point is regarded as determinate. The cardinal points of any figure determined by a Euclidean construction are always found by means of a finite number of successive applications of some or all of these rules (1), (2) and (3). Whenever one of these rules is applied it must be shown that it does not fail to determine the point. Euclid's own treatment is sometimes defective as regards this requisite. In order to make the practical constructions which correspond to these three Euclidean modes of determination, correponding to (1) the ruler is required, corresponding to (2) both ruler and compass, and corresponding to (3) the compass only. ...it is possible to develop Euclidean Geometry with a more restricted set of postulations. For example it can be shewn that all Euclidean constructions can be carried out by means of (3) alone..."

"The objects of abstract Geometry possess in absolute precision properties which are only approximately realized in the corresponding objects of physical Geometry."

"In the year 1775, the Paris Academy found it necessary to protect its officials against the waste of time and energy involved in examining the efforts of circle squarers. It passed a resolution... that no more solutions were to be examined of the problem of the duplication of the cube, the trisection of the angle, the quadrature of the circle, and the same resolution should apply to machines for exhibiting perpetual motion. an account... drawn up by Condorcet... is appended. It is interesting to remark that the strength of the conviction of Mathematicians that the solution of the problem is impossible, more than a century before an irrefutable proof of the correctness of that conviction was discovered."

"If the question be raised, why such an apparently special problem as the quadrature of the circle, is deserving of the sustained interest which has attained to it, and which it still possesses, the answer is only to be found in a scrutiny of the history of the problem, and especially in the closeness of the connection of that history with the general history of Mathematical Science."

"Success, even in a comparatively limited field, is some compensation for failure in a wider field of endeavour."

"The opinion appears to be gaining ground that this very general conception of functionality, born on mathematical ground, is destined to supersede the narrower notion of causation, traditional in connection with the natural sciences. As an abstract formulation of the idea of determination in its most general sense, the notion of functionality includes and transcends the more special notion of causation as a one-sided determination of future phenomena by means of present conditions; it can be used to express the fact of the subsumption under a general law of past, present, and future alike, in a sequence of phenomena. From this point of view the remark of Huxley that Mathematics "knows nothing of causation" could only be taken to express the whole truth, if by the term "causation" is understood "efficient causation." The latter notion has, however, in recent times been to an increasing extent regarded as just as irrelevant in the natural sciences as it is in Mathematics; the idea of thorough-going determinancy, in accordance with formal law, being thought to be alone significant in either domain."

"The actual evolution of mathematical theories proceeds by a process of induction strictly analogous to the method of induction employed in building up the physical sciences; observation, comparison, classification, trial, and generalisation are essential in both cases. Not only are special results, obtained independently of one another, frequently seen to be really included in some generalisation, but branches of the subject which have been developed quite independently of one another are sometimes found to have connections which enable them to be synthesised in one single body of doctrine. The essential nature of mathematical thought manifests itself in the discernment of fundamental identity in the mathematical aspects of what are superficially very different domains. A striking example of this species of immanent identity of mathematical form was exhibited by the discovery of that distinguished mathematician . . . Major MacMahon, that all possible Latin squares are capable of enumeration by the consideration of certain differential operators. Here we have a case in which an enumeration, which appears to be not amenable to direct treatment, can actually be carried out in a simple manner when the underlying identity of the operation is recognised with that involved in certain operations due to differential operators, the calculus of which belongs superficially to a wholly different region of thought from that relating to Latin squares."

"Who has studied the works of such men as Euler, Lagrange, Cauchy, Riemann, , and Weierstrass, can doubt that a great mathematician is a great artist? The faculties possessed by such men, varying greatly in kind and degree with the individual, are analogous with those requisite for constructive art. Not every mathematician possesses in a specially high degree that critical faculty which finds its employment in the perfection of form, in conformity with the ideal of logical completeness; but every great mathematician possesses the rarer faculty of constructive imagination."

"Much of the skill of the true mathematical physicist and of the mathematical astronomer consists in the power of adapting methods and results carried out on an exact mathematical basis to obtain approximations sufficient for the purposes of physical measurements. It might perhaps be thought that a scheme of Mathematics on a frankly approximative basis would be sufficient for all the practical purposes of application in Physics, Engineering Science, and Astronomy, and no doubt it would be possible to develop, to some extent at least, a species of Mathematics on these lines. Such a system would, however, involve an intolerable awkwardness and prolixity in the statements of results, especially in view of the fact that the degree of approximation necessary for various purposes is very different, and thus that unassigned grades of approximation would have to be provided for. Moreover, the mathematician working on these lines would be cut off from the chief sources of inspiration, the ideals of exactitude and logical rigour, as well as from one of his most indispensable guides to discovery, symmetry, and permanence of mathematical form. The history of the actual movements of mathematical thought through the centuries shows that these ideals are the very life-blood of the science, and warrants the conclusion that a constant striving toward their attainment is an absolutely essential condition of vigorous growth. These ideals have their roots in irresistible impulses and deep-seated needs of the human mind, manifested in its efforts to introduce intelligibility in certain great domains of the world of thought."

"I have said that mathematics is the oldest of the sciences; a glance at its more recent history will show that it has the energy of perpetual youth. The output of contributions to the advance of the science during the last century and more has been so enormous that it is difficult to say whether pride in the greatness of achievement in this subject, or despair at his inability to cope with the multiplicity of its detailed developments, should be the dominant feeling of the mathematician. Few people outside of the small circle of mathematical specialists have any idea of the vast growth of mathematical literature. The Royal Society Catalogue contains a list of nearly thirty-nine thousand papers on subjects of Pure Mathematics alone, which have appeared in seven hundred serials during the nineteenth century. This represents only a portion of the total output, the very large number of treatises, dissertations, and monographs published during the century being omitted."

"A great department of thought must have its own inner life, however transcendent may be the importance of its relations to the outside. No department of science, least of all one requiring so high a degree of mental concentration as Mathematics, can be developed entirely, or even mainly, with a view to applications outside its own range. The increased complexity and specialisation of all branches of knowledge makes it true in the present, however it may have been in former times, that important advances in such a department as Mathematics can be expected only from men who are interested in the subject for its own sake, and who, whilst keeping an open mind for suggestions from outside, allow their thought to range freely in those lines of advance which are indicated by the present state of their subject, untrammelled by any preoccupation as to applications to other departments of science. Even with a view to applications, if Mathematics is to be adequately equipped for the purpose of coping with the intricate problems which will be presented to it in the future by Physics, Chemistry and other branches of physical science, many of these problems probably of a character which we cannot at present forecast, it is essential that Mathematics should be allowed to develop freely on its own lines."

"Perhaps the least inadequate description of the general scope of modern Pure Mathematics—I will not call it a definition—would be to say that it deals with form, in a very general sense of the term; this would include algebraic form, functional relationship, the relations of order in any ordered set of entities such as numbers, and the analysis of the peculiarities of form of groups of operations."

"The second part of the book... contains an exposition of the first principles of the theory of complex quantities; hitherto, the very elements of this theory have not been easily accessible to the English student, except recently in Prof. Chrystal's excellent treatise on Algebra. The subject of Analytical Trigonometry has been too frequently presented to the student in the state in which it was left by Euler, before the researches of Cauchy, Abel, Gauss, and others, had placed the use of imaginary quantities, and especially the theory of infinite series and products, where real or complex quantities are involved, on a firm scientific basis. In the Chapter on the exponential theorem and logarithms, I have ventured to introduce the term "generalized logarithm" for the doubly infinite series of values of the logarithm of a quantity."

"The history of mathematics cannot with certainty be traced back to any school or period before that of the…Greeks…. Though all early races …knew something of numeration yet the rules…were neither deduced from nor did they form part of any science."

"The great masters of modern analysis are Lagrange, Laplace, and Gauss, who were contemporaries. It is interesting to note the marked contrast in their styles. Lagrange is perfect both in form and matter, he is careful to explain his procedure, and though his arguments are general they are easy to follow. Laplace on the other hand explains nothing, is indifferent to style, and, if satisfied that his results are correct, is content to leave them either with no proof or with a faulty one. Gauss is as exact and elegant as Lagrange, but even more difficult to follow than Laplace, for he removes every trace of the analysis by which he reached his results, and studies to give a proof which while rigorous shall be as concise and synthetical as possible."

"It was, however, from Spain, and not from Arabia, that a knowledge of eastern mathematics first came into western Europe. The Moors had established their rules in Spain in 747, and by the tenth or eleven century had attained a high degree of civilisation."

"Babbage was one of the founders of the Cambridge Analytical Society whose purpose he stated was to advocate "the principles of pure d-ism as opposed to the dot-age of the university."

"The quality of the human mind, considered in its collective aspect, which most strikes us, in surveying this record, is its colossal patience."

"We are able to appreciate the difficulties which in each age restricted the progress which could be made within limits which could not be surpassed by the means then available; we see how, when new weapons became available, a new race of thinkers turned to the further consideration of the problem with a new outlook."

"In the third period, which lasted from the middle of the eighteenth century until late in the nineteenth century, attention was turned to critical investigations of the true nature of the number π itself, considered independently of mere analytical representations. The number was first studied in respect of its rationality or irrationality, and it was shown to be really irrational. When the discovery was made of the fundamental distinction between algebraic and transcendental numbers, i.e. between those numbers which can be, and those numbers which cannot be, roots of an algebraical equation with rational coefficients, the question arose to which of these categories the number π belongs. It was finally established by a method which involved the use of some of the most modern of analytical investigation that the number π was transcendental. When this result was combined with the results of a critical investigation of the possibilities of a Euclidean determination, the inferences could be made that the number π, being transcendental, does not admit of a construction either by a Euclidean determination, or even by a determination in which the use of other algebraic curves besides the straight line and the circle are permitted. The answer to the original question thus obtained is of a conclusive negative character; but it is one in which a clear account is given of the fundamental reasons upon which that negative answer rests."

"The second period, which commenced in the middle of the seventeenth century, and lasted for about a century, was characterized by the application of the powerful analytical methods provided by the new Analysis to the determination of analytical expressions for the number π in the form of convergent series, products, and continued fractions. The older geometrical forms of investigation gave way to analytical processes in which the functional relationship as applied to the trigonometrical functions became prominent. The new methods of systematic representation gave rise to a race of calculators of π, who, in their consciousness of the vastly enhance means of calculation placed in their hands by the new Analysis, proceeded to apply the formulae to obtain numerical approximations to π to ever larger numbers of places of decimals, although their efforts were quite useless for the purpose of throwing light upon the true nature of that number. At the end of this period no knowledge had been obtained as regards the number π of the kind likely to throw light upon the possibility or impossibility of the old historical problem of the ideal construction; it was not even definitely known whether the number is rational or irrational. However, one great discovery, destined to furnish the clue to the solution of the problem, was made at this time; that of the relation between the two numbers π and e, as a particular case of those exponential expressions for the trigonometrical functions which form one of the most fundamentally important of the analytical weapons forged during this period."

"The first period embraces the time between the first records of empirical determinations of the ratio of the circumference to the diameter of a circle until the invention of the Differential and Integral Calculus, in the middle of the seventeenth century. This period, in which the ideal of an exact construction was never entirely lost sight of, and was occasionally supposed to have been attained, was the geometrical period, in which the main activity consisted in the approximate determination of π by the calculation of the sides or the areas of regular polygons in- and circum-scribed to the circle. The theoretical groundwork of the method was the Greek method of Exhaustions. In the earlier part of the period the work of approximation was much hampered by the backward condition of arithmetic due to the fact that our present system of numerical notation had not yet been invented; but the closeness of the approximations obtained in spite of this great obstacle are truly surprising. In the later part of this first period methods were devised by which the approximations to the value of π were obtained which required only a fraction of the labour involved in the earlier calculations. At the end of the period the method was developed to so high a degree of perfection that no further advance could be hoped for on the lines laid down by the Greek Mathematicians; for further progress more powerful methods were required."

"The history of our problem falls into three periods marked out by fundamentally distinct differences in respect of method, of immediate aims, and in equipment in possession of intellectual tools."

"The rapid establishment of Christianity must therefore have been from the conviction which those who embraced it, had of its "Truth and power unto salvation." Christianity at first spread itself amongst the most enlightened nations of the earth - in those places where human learning was in its greatest perfection; and, by the force of the evidence which attended it, amongst such men it gained an establishment. It has been justly observed, that "it happened very providentially to the honour of the Christian religion, that it did not take its rise in the dark illiterate ages of the world, but at a time when arts and sciences were t their height, and when there were men who made it the business of their lives to search after truth and lift the several opinions of the philosophers and wise men, concerning the duty, the end, and chief happiness of reasonable creatures." Both the learned and the ignorant alike embraced its doctrines; the learned were not likely to be deceived in the proofs which were offered; and the same cause undoubtedly operated to produce the effect upon each. But an immediate conversion of the bulk of mankind, can arise only from some proofs of a ddivine authority offering themselves immediately to the senses; the preaching of any new doctrine, if lest to operate only by its own force, would go but a very little way towards the immediate conversion of the gnorant, who have no principle of action but what arises from habit, and whose powers of reasoning are insufficient to correct their errors. When Mahomet was required by his followers to work a miracle for their conviction, he always declined it; he was too cautious to trust to an experiment, the success of which was scarcely whithin the bounds of probablity; he amused his followers with prtended visions, which with the aid afterwards of the civil and military powr; and as the accomplishment of that event was by a few obscure persons, who founded their pretentions upon authority from heaven, we are next to consider, what kind of proofs of their divine commission they offered to the world; and whether they themselves could have been deceived, or mankind could have been deludded by them."

"A very eminent writer has observed, that "the conversion of the Gentile world, whether we consider the difficulties attending it, the opposition made to it, the wonderful work wrought to accomplish it, or the happy effects and consequences of it, may be considered as a more illustrious evidence of God's power, than even our Saviour's miracles of casting out devils, healing the sick, and raising the dead." Indeed, a miracle said to have been wrought without any attending circumstances to justify such an exertion of divine power, could not easily be rendered credible ; and our author's argument proves no more. If it were related, that about 1700 years ago, a man was raised from the dead, without its answering any other end than that of restoring him to life, Iconfess that no degree of evidence could induce me tobelieve it; but if the moral government of God appeared in that event, and there were circumstances attending it which could not be accounted for by any human means, the fact becomes credible. When two extraordinary events are thus connected, the proof of one established the truth of the other. Our author has reasoned upon the fact as standing alone, in which case it would not be easy to disprove some of his reasoning; but the fact should be considered in a moral view - as connected with the establishment of a pure religion, and it then becomes credible. In the proof of any circumstance, we must consider every principle which tends to establish it; whereas our author, by considering the case of a man said to have been raised from the dead, simpli in a physical point of view, without any reference to a moral end, endavours to show that it cannot be rendered credible; and, from such principles, we may admit his conclusions without affecting the credibility of Christianity. The general principle on which he establishes his argument, is not the great foundation upon which the evidence of Christianity rests. He says, "Notestimony can be sufficient to establish a miracle, unless it be of such a kind, that the falsehood would be more miraculous than the fact which it endavours to prove." Now this reasoning, at furthest, can only be admitted in those cases where the fact has nothing but testimony to establish it. But the proofs of Christianity do not rest simply upon the testimony of its first promulgators, and that of those who were affterwards the instruments of communicating it; but they rest principally upon the acknowledged and very extraordinary affects which were produced by the preaching of a few unlearned, obscure persons, who taught "Christ crucified;" and it is upon these indisuptable matters of ffact which we reason; and when the effects are totally unaccountable upon any principle which we can collect from the operation of human means, we must either admit miracles, or admit an effect without an adequate cause. Also, when the proof of any position depends upon arguments drawn from various sources, all concutring to establish its turh, to select some one circumstance, and atrempt to show that that alone is not sufficient to render the fact credible, and thence infer that it is not ture, is a conclusion not to be admitted. But it is thus that our author has endavoured to destroy the credibiliry of Christianity, the evidences of which depend upon a great variety of circumstances and facts which are indisputably true, all cooperating to confirm its truth; but an examination of these falls not whithin the plan here proposed. He rests all his arguments upon the extraordinary nature of the fact, considered alone by itself; for a common fact, with the same evidence, would immediately be admitted. I have endavoured to show, that the extraordinary nature, as much as the mosst common events are necessary to fulfill the usual dispensations of Providence, and therefore the Deity was then direted by the same motive as in a more ordinary case, that of affording us such assitance as our moral condition renders necessary. In the establishment of a pur religion, the proof of its divine origin may require some very extraordinary circumstances which may never afterwards be requisite, and accordingly we find that they have not happened. Here is therefore a perfect concistencty in the operation of the Deity, in his moral government, and not a violation of the laws of nature: Secondly, the fact is immediately connected with others which are indisputably true, and which, without the supossition of the truth of that fact, would be, at least, equally miraculous. Thus I conceive the reasoning of our author to be totally inconclusive; and the argumentss which have been employed to prove the fallacy of his conclusions, appear at the same time, fully to justify our belief in, and prove the moral certainty of, our holy religion."