The Marquis de Laplace, peer of France, one of the forty of the French Academy, member of the Academy of Sciences and of the Bureau of Longitude, Associate of all the great Academies or Scientific Societies of Europe, was born at Beaumont-en-Auge, of parents belonging to the class of small farmers, on the 28th of March, 1749; he died on the 5th of March, 1827. The first and second volumes of the 'Mécanique Céleste' [Mechanism of the Heavens] were published in 1799; the third volume appeared in 1802, the fourth in 1805; part of the fifth volume was published in 1823, further books in 1824, and the remainder in 1825. The 'Théorie des Probabilités' was published in 1812. We shall now present the history of the principal astronomical discoveries contained in these immortal works. Astronomy is the science of which the human mind may justly feel proudest. It owes this pre-eminence to the elevated nature of its object; to the enormous scale of its operations; to the certainty, the utility, and the stupendousness of its results. From the very beginnings of civilization the study of the heavenly bodies and their movements has attracted the attention of governments and peoples. The greatest captains, statesmen, philosophers, and orators of Greece and Rome found it a subject of delight. Yet astronomy worthy of the name is a modern science: it dates from the sixteenth century only. Three great, three brilliant phases have marked its progress. In 1543 the bold and firm hand of Copernicus overthrew the greater part of the venerable scaffolding which had propped the illusions and the pride of many generations. The earth ceased to be the centre, the pivot, of celestial movements. Henceforward it ranged itself modestly among the other planets, its relative importance as one member of the solar system reduced almost to that of a grain of sand.