Caille, Nicholas Lewis De La

, an eminent French Inathematician and astronomer, was born at Rumigiiy in the diocese of Rheims on March 15, 1713. His father having quitted the army, in which he had served, amused himself in his retirement with studying mathematics and mechanics, in which he proved the author of several inventions of considerable use to the public. From this example of his father, our author “almost in his infancy took a fancy to mechanics, which proved of signal service to him in his maturer years. At school he discovered early tokens of genius. He came to Paris in 1729; where he studied the classics, philosophy, and mathematics, and afterwards divinity in the college de Navarre, with a view to the church, but he never entered into priest’s orders, apprehending that his astronomical studies, to which he had become much devoted, might too much interfere with his religious duties. His turn for astronomy soon connected him with the celebrated Cassini, who procured him an apartment in the observatory; where, assisted by the counsels of this master, he soon acquired a name among the astronomers, in 1739 he was joined with M. Cassini de Thury, son to M. Cassini, in verifying the meridian through the whole extent of France; and in the same year he was, named professor of mathematics in the college of Mazarine. In 1741 or author was admitted into the academy of sciences as an adjoint member for astronomy and had | many excellent papers inserted in their memoirs; beside which he published several useful treatises, viz. Elements of Geometry, Astronomy, Mechanics, and Optics. He also carefully computed all the eclipses of the sun and moon that had happened since the Christian sera, which were printed in the work entitled” L’Art de verifier les dates,“&c. Paris, 1750, 4to. He also compiled a volume of astronomical ephemerides for the years 1745 to 1755; another for the years 1755 to 1765 and a third for the years 1765 to 1775 as also the most correct solar tables of any; and an excellent work entitled” Astronomic fundamenta novissimis solis et stellarum observationibus stabilita."

Having gone through a seven years series of astronomical observations in his own observatory in the Mazarjne college, he formed the project of going to observe the southern stars at the Cape of Good Hope. This expedition being countenanced by the court, he set out in 1750, and in the space of two years he observed there the places of about ten thousand stars in the southern hemisphere that are not visible in our latitudes, as well as many other important elements, viz. the parallaxes of the sun, moon, and some of the planets, the obliquity of the ecliptic, the refractions, &c. Having thus executed the purpose of his voyage, and no present opportunity offering for his return, he thought of employing the vacant time in another arduous attempt; no less than that of taking the measure of the earth, as he had already done that of the heavens. This indeed had been, done before by different sets of learned men both in Europe and America; some determining the quantity of a degree at the equator, and others at the arctic circle: but it had not as yet been decided whether in the southern parallels of latitude the same dimensions obtained as in the northern. His labours were rewarded with the satisfaction he wished for; having determined a distance of 410,814 feet from a place called Klip-Fontyn to the Cape, by means of a base of 38,802 feet, three times actually measured: whence he discovered a new secret of nature, namely, that the radii of the parallels in south latitude are not the same length as those of the corresponding parallels in north latitude. About the 23d degree of south latitude he found a degree on the meridian to contain 342,222 Paris feet. The court of Versailles also sent him an order to go and fix the situation of the Isles of France and of Bourbon. While at the Cape too he observed a wonderful effect of the atmosphere | in some states of it although the sky at the Cape be generally pure and serene, yet when the south-east wind blows, which is pretty often, it is attended with some strange and even terrible effects: the stars look larger, and seem to dance; the moon has an undulating tremor; and thr planets have a sort of beard like comets.

M. de la Caille returned to France in the autumn of 1754, after an absence of about four years; loaded, not with the spoils of the east, but with those of the southern heavens, beiore then almost unknown to astronomers. Upon his return, he first drew up a reply to some strictures which the celebrated Euler had published relative to the meridian: after which he settled the results of the comparison of his observations for the parallaxes, with those of other astronomers that of the sun he fixed at 9|“; of the naoon at 56 56”; of Mars in his opposition, 36“of Venus 3.” He also settled the laws by which astronomical refractions are varied by the different density or rarity of the air, by heat or cold, and by dry ness or moisture. And lastly he shewed an easy and practicable method of finding the longitude at sea, by means of the moon. His fame being now celebrated every where, M. de la Caille was soon elected a member of most of the academies and societies of Europe, particularly of those of London, Bologna, Petersburg!], Berlin, Stockholm, and Gottingen. In 1760 he was attacked by a severe fit of the gout, which, however, did not interrupt the course of his studies; for he then planned out a new and large work, no less than a history of astronomy through all ages, with a comparison of the ancient and modern observations, and the construction and use of the instruments employed in making them. Towards the latter part of 1761, his constitution became greatly reduced; though his mind remained unaffected, and he resolutely persisted in his studies to the last. He died March 21, 1762, in the forty-ninth year of his age. Besides the publications before mentioned, he had a vast number inserted in the Memoirs of the French academy, from 1711 to 1763. In most of the volumes of those years are two or more of his papers. ¹