Alembers (a-lon-bare'), Jean le Rond d', a celebrated man of letters and a mathematician. The natural son of Madame de Tencin and the poet Destouches, was born in 1717. He was the friend of Voltaire, and acquired high esteem by his works, which fill eighteen volumes. His treatises on dynamics and fluids at once established for him a reputation in science. Died, 1783.