BORDA, Jean Charles, mathematician and nautical astronomer, was born at Dax on the 4th May 1733. He studied at La Flèche, and at an early age obtained a commission in the cavalry. In 1756 he presented a valuable paper to the Academy of Sciences, who elected him a member. He was present at the battle of Hastembeck, and soon afterwards joined the naval service. He visited the Azores and the Canary Islands, of which he constructed an admirable map. In 1782 his frigate was taken by a British squadron; he himself was carried to England, but was almost immediately released on parole, and returned to France. He died on the 20th February 1799. Borda was an admirable mathematician, and contributed a long series of valuable memoirs to the Academy of Sciences. His researches in hydrodynamics were highly useful for marine engineering, while the reflecting and repeating circles, as improved by him, were of great service in nautical astronomy. He was associated with Delambre and Méchain in the attempt to determine an arc of the meridian, and the greater number of the instruments employed in the task were invented by him. (See Biot, “Notice sur Borda” in the Mem. de l , Acad. des Sciences, iv.)