1911 Encyclopædia Britannica/Lacaille, Nicolas Louis de

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LACAILLE, NICOLAS LOUIS DE (1713–1762), French astronomer, was born at Rumigny, in the Ardennes, on the 15th of March 1713. Left destitute by the death of his father, who held a post in the household of the duchess of Vendôme, his theological studies at the Collège de Lisieux in Paris were prosecuted at the expense of the duke of Bourbon. After he had taken deacon’s orders, however, he devoted himself exclusively to science, and, through the patronage of J. Cassini, obtained employment, first in surveying the coast from Nantes to Bayonne, then, in 1739, in remeasuring the French arc of the meridian. The success of this difficult operation, which occupied two years, and achieved the correction of the anomalous result published by J. Cassini in 1718, was mainly due to Lacaille’s industry and skill. He was rewarded by admission to the Academy and the appointment of mathematical professor in Mazarin college, where he worked in a small observatory fitted for his use. His desire to observe the southern heavens led him to propose, in 1750, an astronomical expedition to the Cape of Good Hope, which was officially sanctioned, and fortunately executed. Among its results were determinations of the lunar and of the solar parallax (Mars serving as an intermediary), the first measurement of a South African arc of the meridian, and the observation of 10,000 southern stars. On his return to Paris in 1754 Lacaille was distressed to find himself an object of public attention; he withdrew to Mazarin college, and there died, on the 21st of March 1762, of an attack of gout aggravated by unremitting toil. Lalande said of him that, during a comparatively short life, he had made more observations and calculations than all the astronomers of his time put together. The quality of his work rivalled its quantity, while the disinterestedness and rectitude of his moral character earned him universal respect.

His principal works are: Astronomiae Fundamenta (1757), containing a standard catalogue of 398 stars, re-edited by F. Baily (Memoirs Roy. Astr. Society, v. 93); Tabulae Solares (1758); Coelum australe stelliferum (1763) (edited by J. D. Maraldi), giving zone-observations of 10,000 stars, and describing fourteen new constellations; “Observations sur 515 étoiles du Zodiaque” (published in t. vi. of his Éphémérides, 1763); Leçons élémentaires de Mathématiques (1741), frequently reprinted; ditto de Mécanique (1743), &c.; ditto d’Astronomie (1746), 4th edition augmented by Lalande (1779); ditto d’Optique (1750), &c. Calculations by him of eclipses for eighteen hundred years were inserted in L’Art de vérifier les dates (1750); he communicated to the Academy in 1755 a classed catalogue of forty-two southern nebulae, and gave in t. ii. of his Éphémérides (1755) practical rules for the employment of the lunar method of longitudes, proposing in his additions to Pierre Bouguer’s Traité de Navigation (1760) the model of a nautical almanac.

See G. de Fouchy, “Éloge de Lacaille,” Hist. de l’Acad. des Sciences, p. 197 (1762); G. Brotier, Preface to Lacaille’s Coelum australe; Claude Carlier, Discours historique, prefixed to Lacaille’s Journal historique du voyage fait au Cap (1763); J. J. Lalande, Connoissance des temps, p. 185 (1767); Bibl. astr. pp. 422, 456, 461, 482; J. Delambre, Hist. de l’astr. au XVIIIe siècle, pp. 457-542; J. S. Bailly, Hist. de l’astr. moderne, tomes ii., iii., passim; J. C. Poggendorff, Biog. Lit. Handwörterbuch; R. Grant, Hist. of Physical Astronomy, pp. 486, &c.; R. Wolf, Geschichte der Astronomie. A catalogue of 9766 stars, reduced from Lacaille’s observations by T. Henderson, under the supervision of F. Baily, was published in London in 1847.