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nomy, nay one of the greatest men that ever appeared on earth. Our Author is not the firft who has spoken of Kepler with enthufiafm, though perhaps he goes too far, when he exalts him above Copernicus and Ticho-Brahe; who, he affirms, could have no advantage over the ancient founders of astronomy, of whofe labours we have fome remains in the tables of the Perfians, Indians and Siamefe; whereas Kepler deftroyed the edifice of the ancients to erect another more permanent and more fublime. There is no doubt of Kepler's extraordinary genius, difcoveries and merit: but if Copernicus had no advantage over the ancient founders of aftronomy, what could induce our Author to call his labours the epocha of a grand revolution in afronomy in the preceding volume, and to fay in this, when he is introducing Kepler, that at the first appearance of the Copernican system, truth was new and without fupport, and flood in need of fuch a genius as Kepler to difcern its grandeur? All this is not very confiftent.-If in affirming that Copernicus had no advantage over the ancient aftronomers, he has in view bis ancient primitive nation, the faultless monfter which the world ne'er faw,-which had brought aftronomy and the other sciences to perfection, and of whofe fcience Copernicus and the reft had only recovered fome fragments, he may, in this refpect, fay the same thing of Kepler that he did of Copernicus ;-and if he has not in view this primitive nation, but the aftronomers whofe names and labours have come down to us from an early antiquity, then it is not true that Copernicus, Ticho-Brahe, and others of that clafs had no advantage over the ancient founders of aftronomy.
Be that as it may, Kepler was, indeed, a luminary of the first magnitude in the aftronomical world, and there were even streaks of genius in his moft extravagant fingularities. Defcartes, Gregory, and even the immortal Newton acknowledge their obligations to him, on many occafions; and he will certainly be revered, as long as true genius and aftronomical fcience remain in esteem among men. Kepler adopted, without hesitation, the Copernican fyftem; but he went much farther: he difcovered the true forms of the planetary orbits, proved that they were elliptical, and not circular; and it is this difcovery, that, according to M. BAILLY, fet aftronomy on a new and folid bafis, annihilated the fyftem of the ancients, and went even beyond the fcience of the famous primitive people, who, by what we can learn (fays our Author) from the velhiges of antiquity, had got no farther than the knowledge of circular motions. Kepler's genius and labours are admirably defcribed and appreciated by our learned, ingenious and eloquent Author:-he fhews us this great man in all his afpećts, dicovering the proportions of the celeftial orbits, and thofe laws of their motions that laid the foun
dations of the Newtonian aftronomy, creating a new science of optical aftronomy, composed of the motion of the stars and the phenomenon of light by which it is perceived-perfecting, by this application of optics to aftronomy, the theory of eclipfes, making discoveries which feemed to require the use of the telescope, before that inftrument was invented-affociating natural philofophy to aftronomy-applying the principles of metaphyfics to explain the phenomena of motion-with many other effential operations and improvements in aftronomical science, which the curious Reader will certainly be defirous of perufing in the work itself.
M. BAILLY fufpends his account of the labours of Kepler, in order to introduce his cotemporary and rival Galilei, who was born at Pifa, in 1564, who laid the foundations and unfolded the elementary truths, on which Newton created the fublime theory of motion, difcovered the laws of accelerated motion in falling bodies, and enriched aftronomical fcience with a multitude of other discoveries, which were greatly facilitated by his invention of the telescope, or at least by his application of it to aftronomical ufes.-It is one of thofe circumstances that would afflict humanity, if man's principal deftination looked no farther than the prefent ftate of things, that Kepler lived and died in indigence, and that Galilei was perfecuted.
In the third book our Author treats, first, of the aftronomers that were the cotemporaries of Kepler and Galilei, and afterwards of their fucceffors. Here we meet with an account of the labours of Longomontanus, a Dane, Albert Curtius, Father Scheiner, a Jefuit (who was the first that attended to, or at leaft explained the elliptical form that the fun affumes in his approach to the horizon), de Rheita, Bayer of Augsburg, Robert Fiudd, and Horrox, the firit who obferved the paffage of Venus, and seemed to have been born for that object alone. Horrox lived in the obscurity of retirement, and the filence of study, and at the age of twenty-two, when he died, he had already the foundest notions and the most extensive knowledge of physical attronomy. Vendelinus, Snellius, Blaeu, Hortenuus, Cavalieri, Fontana, the learned and indefatigable compiler Riccioli, Peyreíc, and others of inferior note, are alío treated in this book.
Book fourth.-Deftortes (lays M. BAILLY), who taught us to think, who broke the yoke of authority, and would admit no truths before they were examined with precision and afcertained by evidence, is one of thofe philofophers who produced the greatest number of errors. The parallel, or rather contraft, in which he reprefents the different methods followed by Bacon and Defcartes in the investigation of truth, is beautiful, ingenious and folid; and though it contains, in fubftance, what has been often faid of these two great men, yet it has an afpect of
novelty by that luminous arrangement of ideas, and that unequalled felicity of expreffion, that reign through this whole. work, and are particularly confpicuous in this fourth book.
As to the merit of Defcartes in aftronomical science, it is confiderable; he opened a path to the most interesting discoveries by his geometrical inventions, and he difcovered, in effect, that centrifugal force which is an agent of fuch importance in the motion of the celestial bodies; but he neither decompounded it, nor investigated the forces that confpire to produce it, nor difcerned the power that retains, counterbalances, and modifies it. His hypothefes in dioptrics and other branches of natural philofophy are admirably appreciated and criticised in the reft of this book; in which we find interesting digreffions from the main fubject of the work before us.
The fifth book contains an account of Bouillaud, Hevelius, Huygens, and fome other aftronomers, fuch as Ward, Street, Rook, Wing, Mercator, Linemann, and Langrenus. The celebrated Chriftian Huyghens appears here in all his luftre;-his improvements of the telescope, his discovery of Saturn's ring and of one of his fatellites; his pendulum, his writings, give him an eminent rank among aftronomers.
The fixth book exhibits the erection of academies, and the invention of inftruments; and in the seventh our Author treats of the methods of obferving the heavenly bodies.-This book is learned, full of matter, and incapable of being even fuperficially abridged. The principal object of the eighth book is the celebrated F. D. Caffini, who was born at Perinaldo in the county of Nice, in the year 1625, whofe tables of the motions of the fatellites, and other aftronomical difcoveries and improvements, procured him a high reputation, and an honourable fettlement in France, under the protection of Lewis XIV, and Colbert. In the ninth book M. Bailly treats of the measure of the earth, and of the voyages that have been undertaken in France for the improvement of aftronomy; and in the tenth he enumerates the labours and discoveries of many eminent aftronomers about the fame time. The eleventh book contains the labours of Flamftead, Halley and Hook (which laid the foundations of aftronomy in England), and the difcoveries that were made in that fcience from the year 1672 to 1686.
Newton, and Newton alone, employs the head, heart, imagination, and pen of our excellent Author in the twelfth book, which contains above one hundred and ten pages, and in which, not only, nothing is omitted, but all the rays, that were blended in the luftre of that immortal man, are diftinguished by M. BAILLY, and are collected here in all their glow of light and truth. There is a certain tone of eloquent fimplicity, gravity and dignity in this book, that is worthy of its fubject, and does
fingular honour to its Author. He praifes Newton with pleas fure, knowledge, admiration and eafe. He confiders all ftudied ornaments in his expreffions, as beneath the dignity of the EngJith philofopher, who was fingularly modeft, did great things with fimplicity, and followed Nature. Newton, no doubt, is well known;-but thofe who know him moft will certainly perufe this part of M. BAILLY's work with the greatest pleasure; and what ample inftruction, what a fund of admiration will it not yield to those who are not acquainted with all the wonders of this man's genius, and all the excellence and fimplicity of his heart?" I fhall fay nothing of his ftudies (these are the words of our Author); he seems rather to have discovered, than ftudied, and it may be almoft faid, that he acquired knowledge by intuition. He ran through the elements of Euclid: the bare mention of the theorems laid open to him their demonftrationi, and he proceeded to the geometry of Defcartes, where he dif cerned the language of a great genius, and ideas proportioned to his own capacity and powers. No mistake, no errors have yet been discovered in his writings; accordingly, Fontenelle applies to him the witty thought of an ancient writer concerning the majestic river that fertilizes Egypt, and whofe source was fo long unknown, il n'a pas été permis aux hommes de voir le Nil foible et naiffant.”
After having remarked, that it was referved for Newton to demonftrate the caufes of gravity, and to fecure that important dif covery upon the foundation of mathematical, certainty, M. BAILLY enters into an ample detail concerning the fyftem of attraction, and all the other difcoveries of that tranfcendent genius. "His refearches were admired-many, however, entertained doubts with refpect to their refults: time and long. tudy were requifite in order to understand him, and to render even the most knowing worthy to receive his leffons.". -We need not enter into our Author's enumeration of the fublime contents of the Newtonian philofophy; but we cannot resist the pleafure of making a few extracts from the portrait of the Englith philofopher, with which the Author concludes this twelfth book.
"Newton, fays he, is as fingular by the character of his genius, as by his fublime difcoveries; it was gold without alloy, perfectly pure. Genius, by its nature, is ardent, vehement, and the need in which it ftands of motion, feems to be the fpring which makes it foar. But the genius of Newton was vaft without the ardor of paffion, and calm without lofing aught of its activity.-The objects and ideas which other mortals purfue with fuch agitation, pain and effort, feem to have offered themselves to the intuition of this great man, who exhibits to us the image of an obferver, fixed and motionlefs, who fees fucceffively
ceffively the whole heavens unfolding, around him, their properties and powers.-The genius of Newton feems to have transported him to the center of nature-to the point where all the rays of truth converge and terminate; there he became a fimple fpectator, and has related what he faw.What a distance is there between him and his great forerunners, both with respect to extent and accuracy of ideas! Their luftre was always more or lefs tarnished by errors--Newton produces nothing but truths.".
The fimplicity and modefty of Newton were the confequences of his fuperiority; men of that order execute with facility the most difficult things; how then fhould they admire what has coft them fo little pain and effort?. Men applaud themselves most, when they are surprised at their productions; they fet a high value on the fruits of painful efforts;-pride is the indication of mediocrity, and the acknowledgment of our weaknefs."
"One of the circumftances that fhew Newton's difcoveries were (to him) as easy, as they were in themselves important and fublime, is the little pains he was at to infure to himself the honour of having made them. He fufpended the publication of a curious difcovery, because he saw that Mercator was alfo in the way to find it out, and if truth was inveftigated, it was equal to him who made the difcovery. The first hints that were thrown out, questioning the originality of his ideas of light and colours, made him put off, for a great number of years, the publication of his Treatife on Optics, which is a work truly original and full of genius. The dispute, relative to the invention of the method of fluxions, gave him pain, not on account of his being obliged to fhare the honour of this invention with Leibnitz, but because his tranquillity was ruffled in the contest: Newton was defirous of that tranquillity, which is as neceffary to the contemplation of nature as to the enjoyment of life.-Are those minds fit to be employed about the grand objects of nature and the univerfe, which are always acceffible to the petty interefts of vain-glory, and the fumes of literary faction? Time glides along amidst these fhameful divifions, genius pines, and truth escapes through the tumult. Newton defired tranquillity, because he knew what was the true employment of time; he was indifferent about fame, which followed him fpontaneously, and remains infeparably attached to his memory:If, as Plato thought, there is a fcale of beings which terminates in the highest degree of finite perfection, the nearest approach to Deity, the human fpecies has many great men to prefent in this feries; but Newton, accompanied with his pure, intellectual truths, would undoubtedly exhibit the highest degree of force and perfection to which the human mind has ever arifen, and would be