BIOT, JEAN BAPTISTE

(1774-1862), Fr. physicist, prof. of Math’s at Beauvais afterwards prof. of Physics at Collége de France, and of Physical Astron. at Faculté des Sciences; invented polarimeter; pub. researches on polarized light, astron., physics, and other subjects, Edouard Constant B., his s. (1803-1850), authority and writer on Chinese affairs, BIOTITE. A species of mica, known as magnesia mica to distinguish it from potash or muscovite mica. It consists of a compound silicate of aluminum, iron, magnesium and pota ium, and occurs in different varieties of which meroxene, found in volcanic deposits, is the most important. Other varieties and phlogopite. Biotite is usually dark brown or black in color and is transparent only in thin laminae. It is denser than muscovite and le elastic. It is frequently found a ociated with muscovite in granite and other minerals, the two micas being intimately mixed. Meroxene is found in the neighborhood of Mt. Vesuvius. Rubel lane is a red mica, also found in volcanic rocks, and almost entirely lacks elasticity. Lepidomelane is black and is slightly magnetic, probably due to the fact that it is rich in iron.