LEA, HENRY CHARLES, an Amer ican publisher and historian; born in Philadelphia, Pa., Sept. 19, 1825; entered his father's publishing house in 1843; became the principal in 1865; and retired 1880. Between 1840 and 1860 he wrote many papers on chemistry and conchology. After 1857 he devoted his attention to European medimval history, his chief works being: "Superstition and Force" (1866) ; "An Historical Sketch of Sacerdotal Celibacy" (1867); "His tory of the Inquisition of the Middle Ages" (1888) ; "A History of Auricular Confession and Indulgences" (1896) ; "The Moriscos of Spain" (1901); etc. He died in 1909.
LEAD (Greek, mo/ybdos; Latin, plum burn, whence the chemical symbol Pb). This metal was well known to the an cients. Several lead mines in Great 13ritain were worked by the Romans, with whom the leaden waterpipes were common. Lead is of a bluish white color, and is one of the softest of metals. Its ductility and tenacity are low in the scale, but it may be converted into tolerably thin sheets, as well as drawn into wire. It fuses at
325°, and may with difficulty be obtained in cubic or octahedral crystals; sp. gr. 11.38. The lead of commerce is often nearly pure and can be obtained perfectly so by reduction of the pure nitrate. Metallic lead, exposed to the ac tion of air and pure water, is powerfully corroded, and as a result the water is found to have dissolved the oxide of lead. The impurities of most waters modify this tendency by forming a thin film on the surface of the metal and so prevent ing any further oxidation. As a sani tary precaution, slate cisterns are great ly to be preferred to leaden ones, Lead enters into the composition of type-metal, pewter, Britannia metal, and plumbers' solder. The best tests for lead are hyd ric sulphide, which forms a black sul phide, and potassic chromate, which gives a yellow precipitate of lead chromate.