1844.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



333 



^!OTICE OF THE PRINCIPAL ASTRONOMICAL DISCOVE- 

 RIES OF LAPLACE. 

 By M. Arago. 



Translated from the French for He Civil Engineer and Architect's 



Journal, 

 [The accompanying translation gives, from the pen of M. Arago, a 

 sketch not only of the labours of Laplace but also of the progress of 

 astronomy in France. It is extracted from the Annuaire du Bureau 

 des Longitudes, which has just appeared.] 



Introductory Note of M. Arago. 



Being appointed to draw up the report of the Committee of the 

 Chamber of Deputies, which was directed in 1S42 to enquire into a 

 proposal of the Minister of Public Instruction, relative to printing at 

 public expense the works of Laplace, I thought it right to lay down a 

 succint analysis of the principal discoveries of our illustrious country- 

 man. Many persons having expressed, perhaps with too much kind- 

 ness, a wish that this analysis should not be huddled up among the 

 crowd of legislative documents, but that it should appear in the 

 Annuaire, I have availed myself of the opportunity of developing it so 

 as to render it less unworthy of public attention. The scientific part 

 of the report, as presented to the Chamber of Deputies, will be found 

 here complete, the rest it seemed might conveniently be retrenched. 

 In this note I will preserve a few lines of the report, intended to de- 

 scribe the objects of the proposed bill, and to make known the arrange- 

 ments which have been adopted by the three powers (of the legisla- 

 ture). 



"Laplace endowed France, Europe, and the learned world with 

 three magnificent compositions, the Traitc de Mi-canique Celeste, the 

 Exposition du Systfnie du Monde (Exposition of the System of the 

 Universe), and the Theorie Analytique des Probabilites. In the pre- 

 sent day no copy of this latter work is to be found among the book- 

 sellers of Paris. The edition of the Mi-canique Celeste itself will soon 

 be exhausted. We have therefore seen with pain the period at hand 

 when those devoted to the study of the transcendental mathematics, 

 would have been forced, from want of the original work, to obtain 

 from Philadelphia, New York, or Boston, the English translation which 

 the skilful geometrician Bowditch has given of the grand work of our 

 fellow countryman. Let us, however, be able to state that such fears 

 were without foundation. To reprint the Mecanique Celeste is for the 

 family of the illustrious geometrician a pious duty, and Madame de 

 Laplace, so rightfully, so profoundly attentive to everything which can 

 enhance the lustre of the name she bears, had determined on encoun- 

 tering the financial outlay. A small estate, near Pont I'Eveque, was to 

 change hands, and the literary world in France would not have been 

 deprived of the satisfaction which it feels in reckoning its astrono- 

 mical treasures as part of the national language. The approaching 

 republication of the works of Laplace rested on a guarantee not less 

 certain. Yielding at once to filial feeling, to the noble impulse of 

 patriotism, and to the enlightened enthusiasm for brilliant discoveries 

 with which more serious studies had inspired him. General de Laplace 

 had long since prepared to become the publisher of the seven volnmes 

 which must immortalize his father. These are glories too elevated, 

 too splendid for the limits of private transactions; to governments 

 belong the glories of preserving them from indifference or forgetful- 

 ness, of presenting them constantly to sight, of spreading them through 

 a thousand channels, of making them available in fine for the general 

 good. Doubtless the Minister of Public Instruction felt these views, 

 when, on the occasion of an addition of the works of Laplace being 

 rendered necessary, he requested you to substitute the great French 

 family for the personal family of the illustrious geometrician. We 

 give, gentlemen, our full and entire adhesion to this proposal — it 

 emanates from a national feeling which can find no opponents within 

 these walls." 



Astronomy is that science in which the human mind may most justly 

 place its glory. This incontestible pre-eminence is owing to the ele- 

 vation of its ends, the grandeur of its means of investigation, the cer- 

 tainty, the utility, the unheard of magnificence of its results. From 

 the beginning of society the study of the movements of the stars has 

 constantly occupied the attention of governments and people. Many 

 great captains, illustrious statesmen, eminent writers, philosophers, and 

 speakers of Greece and Rome took their delight in it. We must, 

 however, be allowed to say that the astronomy truly worthy of that 

 name is quite a modern science, dating only from the sixteenth cen- 

 tury. 



Three great and brilliant phases have marked its progress. In 

 1543 Copernick broke with a firm and bold hand the greater part of 

 the antique and venerated scaffolding with which the illusions of sense, 



No. 85,— Voi, VIL— September, 1844. 



and the pride of eyes had filled the world. The earth ceased to be 

 the centre and point of the heavenly movements, and was obliged 

 modestly to rank among the planets, while its material importance 

 among the whole bodies which compose our solar system was brought 

 down to that of a grain of sand. 



Twenty-eight years had gone by from the day when the canon of 

 Thorn died, holding in his failing hands the first copy of a work which 

 was to shed on Poland such pure and brilliant glory, when Wittenberg 

 saw the birth of a man fated to produce a revolution in science not 

 less fruitful and yet more difficult. This man was Kepler. Endowed 

 with two qualities, seemingly mutually opposed, a volcanic imagina- 

 tion, and an obstinacy unthwarted by the most fatiguing numerical cal- 

 culation, Kepler divined that the movements of the stars were con- 

 nected together by single laws, or using his own expression, harmonic 

 laws. These laws he undertook to develupe. A thousand fruitless 

 attempts and errors in figures, inseparable from colossal labour, did 

 not prevent him a single moment from moving resolutely toward the 

 end he thought he could foretell. Two and twenty years were em- 

 ployed in this research without any reason for affliction. In truth, 

 what are two and twenty years labour to him who may be the legis- 

 lator of worlds, who will inscribe his name in ineffaceable marks on 

 the front page of an immortal code, and who mav cry in dithyrambic 

 language, without anyone being able to contradict it, "The lot is 

 thrown; I am writing my book ; it will be read bv the present age or 

 by posterity— what matters that ?— it can wait for its reader. Has 

 not God waited six thousand years a contemplator of his work?" 



To seek out a physical cause capable of making the planets run 

 through closed curves ; to place in power the principle of the main- 

 tenance of the world, and not in solid props and in the crystal spheres 

 our ancesters had dreamed ; to extend to the revolutions of the stars 

 the general elements of the mechanism of terrestrial bodies, such were 

 the questions which remained to be solved after Kepler had published 

 his discoveries. Very distinct outlines of these great problems are to 

 be found here and there among ancients and moderns, from Lucretius 

 and Plutarch down to Kepler, BouUiaud and Borelli. To Newton, 

 however, we must award the merit of the solution. That great man, 

 like many of his predecessors, introduced among the celestial bodies 

 a tendency to approach, or attraction, and drew from the laws of 

 Kepler the mathematical character of that power, carried it out to all 

 the material molecules of the solar system, and developed his brilliant 

 discovery in a work which, even now, is the eminent offspring of 

 human intellect. 



The heart collapses when in studying the history of science we find 

 such a magnificent intellectual movement effected without the aid of 

 France. Practical astronomy added to our inferiority. The means of 

 research were in the beginning carelessly given to foreigners, to the 

 detriment of natives full of knowledge and zeal. After, superior minds 

 contended bravely but fruitlessly against the want of ability in our 

 workmen. During this time, Bradley, on the otherside of the channel, 

 more fortunate, gained immortality by finding out aberration and mu- 

 tation. In these admirable revolutions of astronomical science, the 

 quota of France in 1740 was limited to the experimental determina- 

 tion of the flatness of the earth, and finding out the variation in weight. 

 These were two great things, our country however had a tight to re- 

 quire more, for when France does not hold the first rank she has lost 

 her place. That rank, momentarily lost, was brilliantly regained, and 

 we owe it to four geometricians. 



When Newton, giving to his great discovery a generalization which 

 the laws of Kepler did not command, imagined that different planets 

 were not only attracted by the sun, but further, that they were recip- 

 rocally attracted, he placed amid the heavenly space causes which 

 inevitably would disturb the whole. Astronomers could then see wiih 

 the mere eye that in no part of the world, near or far, would the 

 Keplerian law and curve be adequate to the exact delineation of phe- 

 nomena ; and that the simple and regular movements with which 

 ancient dreamers had been pleased to provide the stars, would feel 

 numerous, considerable, and perpetually changing perturbations. To 

 foretell many of these perturbations, to point out the direction, and in 

 a few very rare cases to determine the numerical value, that was the 

 end intended by Newton when be thought of writing his Mathematical 

 Principles of Natural Philosophy. Notwithstanding the incum,iarable 

 wisdom of its author, the Principia only gives a sketch of the planetary 

 perturbations. If that sublime sketch never became a complete view 

 it can never be imputed to want of ardour or of determination; the 

 efforts of the great philosopher were ever superhuman, and tlje ques- 

 tions which he did not solve were insolvable in his day. When the 

 continental mathematicians entered tllefi.'ld, and endeavoured to place 

 on an immoveable base the Newtonian system, and to pertect tliei.reti- 

 cally the astronomical tables, they really found in their way ditficuUies 

 by which the genius of Newton had been driven back, 



28 



