LA. CAILLE, NICHOLAS-LOUIS DE. The following account is almost entirely from Delambre, either from the memoir by him inserted in the 'Biographic UniverseUe; or the ' Hist. de l'Astron. au Memo Siecle.' There are two eloges, one by Grandjean de Fouchy, the other by G. Brotier, prefixed to the 'Ccelum Australe.' As Delembre knew of these eloges, we have not thought it necessary to examine them.
La Caille was born at Rumiguy, near Rosoy, io Thierache, March 15, 1713. His father, a retired military officer, was in the service of the Duchess of Vendome, and was himself attached to science, and endea voured to cultivate the same taste in his son. Ho died however while the latter was at the College of Lisieux, and his son was enabled to continue his studies by the generosity of the Duke of Bourbon. Ile chose theology as his profession; but in passing his first examination he showed so much frankness in his answer to some questions proposed by a doctor of the old school, that this examiner would have refused him his degree but for the remoustrancea of the rest. This incident dis couraged him, and he remained content with the title of abbe, beyond which he never proceeded. lie had previously turned his attentiou to astronomy under great disadvantages ; and upon his renunciation of theology, Fouchy, above mentioned, who relates that his knowledge of astronomy was above all comprehension in so young a person, introduced him to James Cassini, who gave him employment at the Observatory. In the following year, and in conjunction with Maraldi, he made a survey of part of the coast of France, where the talent which he showed occasioned his being employed in the verification of the arc of the meridian. This operation (in which Cassini do Tbury was associated) commenced at the beginning of May 1739, and before the end of the year he had completed the triangulation from Paris to Perpignan, had measured three bases, made the requisite astronomical observations at three stations, and had taken a prominent part in the measurement of a degree of longitude. In the winter of 1740 he extended his operations to the mountains of Auvergne, in order to test some suspicious which he had formed upon the accuracy of Picard's measurement. The result of these labours was the complete establish ment of the gradual increase of the degree in going from the equator to the poles ; which, though long known to be theoretically true, had not previously been confirmed by measuretneut. lu the meanwhile
La Caille had been appointed to a chair of mathematics in the Mazarin College, the duties of which he fulfilled with care, and for which he published treatises on geometry, mechanics, astronomy, and optics He was also employed in the calculation of ephemerides, and in that of eclipses for 1800 years, published in the ' Art de Verifier lee Dates.' In 1746 an observatory was constructed for him at his college, and he began observations on a large scale. The transit instrument being then but little used in France [Caesura], be had no means of judging of its value; eo that with old methods and old instruments he con tinued his career for fourteen years. In 1751 be made his celebrated voyage to the Cape of Good Hope, where he remained four years or something lees. His object was to form a catalogue of southern stars, and up to the present time his results have been in use. He deter mined the places of about ten thousand stars, and grouped them in constellations; measured a degree of the meridian at the Cape, and made a survey of the Mauritius and island of Bourbon. He received for his expenses and those of a clockmaker who accompanied him, all instruments included, 10,000 franca; and so accurately did he keep his accounts, that he was able to explain his expenditure to a sou : it was 9144 francs and five sous, and he insisted on returning the balance in spite of the disinclination of the officers of the treasury to receive it. He returned to Paris in 1754, and occupied himself in the pre paration of his Fundamenta Astronomim, for the publication of which he engaged to furnish a bookseller with almanacs for ten years. He now began to use the transit instrument, but with so much doubt of its accuracy, and consequent repetition of observations, that, according to Delambre, the secondary stars observed by him at this time were determined with a degree of accuracy superior to that of the funda mental stare of other observatories. He also published the posthumous works of Bouguer, a small table of logarithms, and various observations. At the end of 1761 he was seized with gout, but he remained during the winter employed in his observatory, passing most nights upon cold stonea in the act of observing : a fever was the consequence, and he died March 21, 1762, aged forty-nine years. His last act was the return of the instruments which he had borrowed, and the commission of his manuscripts to his friend Maraldi.