whole aperture of the telescope, and from the interval of time which elapsed, lie obtained the values of the diameters of the satellites, which we have given in ASTRONOMY, Table LX. p. 813.
Bailly had long meditated an extensive work on the history of astronomy, and in the year 1775, he completed the first volume of that profound work, entitled, Histoire de l' Astronomie Ancienne. The second and third volumes, entitled, Histoire de l' As tronomie Moderne, appeared in 1779, and the fourth in 1782, which completed the history of ancient and modern astronomy. The return of M. Gentil from India, with a new set of astronomical tables, the epochs of which extend to such a remote period as the year 3102 before Christ, attracted the attention of philosophers to this curious branch of into history of astronomy. These tables were put into the hands of Bailly, who diligently compared them with mo dern observations, and who found that they must either have been constructed from actual observa tion, or that the Indians must have been acquainted with the most refined and intricate theories of physi cal astronomy. The profound researches, the nice calculations, and the ingenious and acute reasonings by which he has supported the antiquity of the In dian astronomy, were published in 1787, in his Trait de l' Astronomze Indienne et Orientate, which com pleted the great work to which his life had been de.. voted,* The Histoire de Astronomie by Bailly, is perhaps one of the most interesting books that has ever been written upon a scientific subject. His ingenious speculations respecting the early history of astrono my ;—the copious brilliancy, of his descriptions ;— the eloquence with which he pleads the cause, and paints the sufferings of neglected genius ;—and the glowing imagery with which his lively fancy every where embellishes the general narrative, throw an air of enchantment round the most common de tails. Even amid the driest enumeration of facts, the attention is perpetually arrested and kept alive by the mo. t delicate touches of nature, and by the nicest discrimination of chaiacter. The loose and scatter ed materials which the history of astronomy often presents, are chained together in one connected narrative, and one astronomer follows another, and new discoveries spring from those which precede them, as if the progress of discovery had been tinder the controul of causes less accidental than those nature has prescribed. But it is ,in those great and general views which constitute the peculiar province of philosophy, that Bailly shines above all praise. In tracing the effects of moral causes and political insti tutions on the advancement of astronomy, and on the general progress of our species ;—in painting the baneful effects of an unholy superstition upon the happiness and improvement of mankind ;—in describ ing those alternate periods of languor and renovation, which accompany the mighty convulsions of nations, which follow the tyranny or munificence of princes, or in which the human mind, without any apparent cause, sinks into torpid inactivity, or soars beyond its wonted flight ;—in marking the connection be tween the various sciences, and estimating the mutual aid which each imparts to the advancement of the rest ;—and in anticipating the conquests which hu man genius has yet to atchieve over vice and error, throughout every region of Nature—Bailly rises to a sublimity of eloquence, which could be inspired only by the powerful interest which he felt for the progress of science, and for the happiness of his fel low creatures.
Besides this extensive work, Bailly published the following papers in the Memoirs of the French Aca demy. " Memoir on the Epochs of the Moon's Motions at the end of the last Century." " On the Comet of 1762." " Astronomical Observations made at Noslon 1764." " On the Eclipse of the Sun of the 1st April 1764." " Observations made at the Louvre, from 1760 to 1764." " On the Cause of the Variation of the Inclination of the Se cond Satellite of Jupiter." " On the Motion of the Nodes, and on the Variation of the Inclination of Ju piter's Satellites." " Essay on the Theory of the Satellites of Jupiter." " Observations on the Op position of the Sun.and Jupiter." " On the Equa tion of Jupiter's Centre," &c. " On the Transit of Venus in 1769, and on the Eclipse of the Sun on the 4th June of the same year." Like D'Alembert, his illustrious contemporary,. Bailly was highly distinguished by his literary at tainments. His Eloge upon Leibnitz, published in 1768, carried off the prize of the Academy of Ber lin, and the eloges which he composed upon Charles. V., Corneille, La Caille, Cook, Moliere, and Gres-. set, extended his reputation as an elegant writer. The speculations contained in the first volume of his History of Astronomy, respecting the early state of Upper Asia, led to a correspondence with Voltaire the substance of which he afterwards, published in two volumes, the first of which was entitled, Lettres sur l'Origine des Sciences, et sur celle des Peuples de l' Asie, Paris, 1777 ; and the second, Lettres. sur Atlantide de Platon,. et sur Ancienne Histoire• de l'Asie, Paris, 1779. These two works, and the Eloges already mentioned, were published in two vo lumes in 1770, under the title of " Discourses and Memoirs;',' and were reprinted in 1790, along with other discourses of Bailly, that had been pronounced when he was President of the National Assembly, and Mayor of Paris. . .