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dations of the Newtonian aftronomy, creating a new science of optical aftronomy, compofed of the motion of the stars and the phenomenon of light by which it is perceived-perfecting, this application of optics to aftronomy, the theory of eclipfes, making discoveries which feemed to require the ufe of the te lescope, before that inftrument was invented-affociating natural philosophy to astronomy-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 science 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 Fludd, and Horrox, the firft who obferved the paffage of Venus, and feemed to have been born for that object alone. Horrox lived in the obfcurity of retirement, and the filence of ftudy, and at the age of twenty-two, when he died, he had already the foundeft notions and the most extensive knowledge of phyfical aftronomy. Vendelinus, Snellius, Blaeu, Hortenfius, Cavalieri, Fontana, the learned and indefatigable compiler Riccioli, Peyrefc, and others of inferior note, are alfo treated in this book.
Book fourth. Defcartes (fays 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 represents the different methods followed by Bacon and Descartes in the investigation of truth, is beautiful, inge nious and folid; and though it contains, in fubftance, what has been often said 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 difcoveries by his geometrical inventions, and he discovered, 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 criticifed 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 discoveries 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 astronomers 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 discoveries 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 diftinguifhed 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 praises Newton with pleas fure, knowledge, admiration and eafe. He confiders all ftudied ornaments in his expreffions, as beneath the dignity of the Englifh 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 (thefe are the words of our Author); he feems rather to have difcovered, than ftudied, and it may be almost 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 difcerned the language of a great genius, and ideas proportioned to his own capacity and powers. No mistake, no errors have yet been difcovered in his writings; accordingly, Fontenelle applies to him the witty thought of an ancient writer concerning the majestic river that fertilizes Egypt, and whose fource 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 difcovery 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. study 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
"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 stands 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 themfelves to the intuition of this great man, who exhibits to us the image of an obferver, fixed and motionlefs, who fees fuc
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 moft, when they are furprised 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 circumstances that fhew Newton's discoveries were (to him) as easy, as they were in themselves important and fublime, is the little pains he was at to insure to himself the honour of having made them. He fufpended the publication of a curious discovery, because he saw that Mercator was also in the way to find it out, and if truth was investigated, it was equal to him who made the difcovery. The firft hints that were thrown out, queftioning the originality of his ideas of light and colours, made him put off, for a great number of years, the publication of his Treatise on Optics, which is a work truly original and full of genius. The difpute, relative to the invention of the method of fluxions, gave him pain, not on account of his being obliged to share 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 necessary 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 shameful divifions, genius pines, and truth efcapes 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 arisen, and would be
fufficient, alone, to affign the place, which human nature ought to hold in this grand fcale."
The thirteenth book treats of the researches and obfervations relative to the planets and the progress of aftronomy, fince the difcoveries of Newton, or from the year 1687 to 1730. The fourteenth contains researches relative to comets and ftars, and the progrefs of aftronomy during the period laft mentioned.
This volume is terminated by M. BAILLY's discourse concerning the nature of luminous and obfcure bodies in the univerfe, and a vocabulary defigned to explain certain aftronomical terms, which may efcape the knowledge of numbers, whom the beauty, perfpicuity, fcience and amenity, that jointly adorn this excellent work, will engage to peruse it.
AR T. VII.
Lettres du Docteur DEMESTE, Correspondant de la Societé Royale de la Medicine, au Docteur Bernard, Sc. Sur la Chymie, &c.-Letters concerning Chymiftry, Chriftallography, Decimafticks *, Lithology, Mineralogy, and Natural Philofophy in general, addreffed to Doctor BERNARD, firft Profeffor of Phyfic at Douay, and Fellow of the Royal Society of London, by Dr. DEMESTE, Correfpondent of the Royal Society of Medicine, &c. with this Infcription: Novus rerum nafcitur ordo. Vol. I. Paris. 1779.
HESE letters are the production of a mafterly writer, and an accurate obferver.-Perfpicuity and precifion, method and order, diftinguifh the manner in which the Author expreffes his ideas; but his difcuffions, like many others of modern times, fhew us, that phyfical theories are as little ascertained, and are not a whit more fufceptible of evidence in the analytic line, than metaphysical ones.
The title fhews the kind of entertainment, which the philoso phical, and more efpecially the chymical Reader, is to expect in these letters. The firft difcuffion we meet with turns upon elementary fubftances, among which fome will be furprised to find, neither fire, nor air, as our Author adopts the hypothesis of Sage, confiders these as mixed bodies, of which the former (compofed of phlogifton and elementary acid) contributes to the formation of the latter, by a combination with the aqueous principle. You fee, gentle Reader, how far the air is from being an element, or fimple principle, upon this hypothefis; it is fo far from being fimple, that it is a double-compound. This notion is illustrated and confirmed with great fagacity and depth of reasoning in three of the letters that compofe this volume, to which we refer the curious Reader.
These elements, which we ftill look upon as dufky beings after all these illuftrations, lead our Author to treat of affinities,
* A new French term for experimental chymistry, and more especially mineralogical experiments.