BIOT, Jean Baptiste, French physicist, was born at Paris, 21st April 1774. After leaving school he served for a short time , in the artillery, but again resumed his studies at the Ecole Polytechnique. He distinguished himself in mathematics, and was appointed to a professorship at Beauvais. There he carried on his researches with the greatest assiduity, and gained the acquaintance and friendship of Laplace, from whom he solicited and obtained the favour of reading the proof-sheets of the Mécanique Céleste. In 1800 he was recalled to Paris as professor of physics at the Collège de France. Three years later he was elected a member of the Academy of Sciences, a distinction rarely accorded to one so young as he was. In 1803 Biot, in concert with Arago, investigated the refracting properties of gases, and in the following year accompanied Gay-Lussac in his balloon ascent. He was again associated with Arago in the great undertaking of the measurement of an arc of the meridian in Spain, and at a later date (1817-18) he crossed over to Britain and m?a-sured carefully the length of the seconds’ pendulum along an arc extending to the extreme north of Shetland. In 1814 he was made a chevalier of the Legion of Honour, an order of which he became a commander in 1849. He was a member of the French Academy and of the Academy of Inscriptions and Belles-Lettres, as well as of most foreign scientific societies. In 1840 he received the Rumford gold medal for his researches in polarized light. He died at an advanced age in 1862. Biot’s researches extended to almost every branch of physical science; bat his greatest discoveries were made in the department of optics, mainly in connection with the polarization of light. He had a thorough command of the best methods of analysis, and ...