Lacaille, Nicolas Louis de (nēkôläˈ lwē də läkäˈyə) [key], 1713–62, French astronomer. As a result of his success in making meridional measurements in France under the patronage of the duke of Bourbon he was elected to the French Academy. He also became professor of mathematics at the Collège Mazarin, where he established an observatory in 1746. He was at the head of an astronomical expedition (1750–54) to the Cape of Good Hope. There he made observations of 10,000 southern stars, recording their positions; made the first measurement of an arc of the meridian of South Africa; and determined the lunar and solar parallax. Among his works are Astronomiae fundamenta (1757), Tables solaires (1758), Coelum australe stelliferum (1763), and Journal historique du voyage fait au cap de Bonne-Esperance (1763).
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