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244 LEACH LEAD cinnati, O." (8vo, Philadelphia, 1849), was pre- pared from his papers by Mr. W. 8. Sullivant. III. Blathew Carey, an American chemist, son of Isaac, born in Philadelphia in 1823. He studied chemistry in the laboratory of Prof. James Booth, and directed his attention to special branches of the science. His first pub- lished papers, in the " American Journal of Sci- ence," were a series of analyses of the coals from the various mines of Pennsylvania and Maryland. These were followed by papers on picric acid and its salts ; on nitrate and nitrite of ethyl ; on the ethyl and methyl ammonias, with their separation and reactions ; on the germination and growth of seeds ; on the pla- tinum metals, with improved methods of sepa- rating them, &c. He is, however, best known by his papers on photographic chemistry. He made a special study of the chemical effects of light, more particularly on the silver haloids, upon which subject he published papers in various scientific periodicals. His "Manual of Photography" (Philadelphia, 1868; 2d ed., 1871) is a work of standard authority among photographers. IV. Henry Charles, an American author, brother of the preceding, born in Phila- delphia, Sept. 19, 1825. He entered into busi- ness at the age of 17, and has been for many years at the head of a large publishing house in Philadelphia. During the civil war he or- ganized the system of municipal bounties to encourage volunteering, and wrote much for periodicals. Since that time he has taken an active part in urging many important measures of political reform. A paper written by him at the age of 14, on the salts of manganese, was published in Silliman's "Journal." He also published papers on fossil and recent con- chology, and wrote largely on literary and critical subjects. About 1857 he directed his special attention to the study of European mediaeval history, and has published "Supersti- tion and Force : Essays on the Wager of Law, the Wager of Battle, the Ordeal, and Torture " (1866 ; enlarged ed., 1870) ; " Historical Sketch of Sacerdotal Celibacy in the Christian Church " (1867); and "Studies in Church History: the Rise of the Temporal Power, Benefit of Clergy, and Excommunication " (1869). He is now (1874) engaged in collecting material for a history of the inquisition. LEACH, William Elford, an English naturalist, born in Plymouth in 1790, died at San Se- bastiano, Piedmont, Aug. 25, 1836. As a boy he loved to make collections of natural objects, and in 1809 he became a student at St. Bar- tholomew's hospital in London, then under the care of Dr. Abernethy. Before the com- pletion of his medical studies he became known as an ardent student in zoology ; and from Edinburgh he was called to London to fill the post of curator of the natural history depart- ment of the British museum. Here he found time to prepare papers for publication in the " Transactions " of the chief scientific societies in Europe and America. One of the first and most important of these was that on " Crns- taceology" (1813), wherein he advocated the separation of the myriopoda, arachnida, and insecta from the Crustacea, which are all grouped by Linnaeus under insecta. His other most important works were the " Zoological Miscellany," a serial commenced in 1814 and completed in 1817, in 3 vols., and the first di- vision of the " History of the British Crusta- cea," of which 17 parts appeared. His severe labors finally so affected his eyesight and his general health that he was obliged to resign his curatorship, and to abandon to a great ex- tent the pursuit of his favorite studies. In 1826 he visited southern Europe, where he made valuable collections of insects, which are pre- served in the Plymouth institution and by the Devon and Cornwall natural history society. He died of cholera. His love of animals was excessive, and he had a peculiar faculty for sub- duing the most ferocious kinds. One of the most faithful and attached companions of his walks was a wolf which he had tamed. LEAD, an elementary substance belonging to the class of metals, and having when pure the following characteristics : color white with bluish gray tint ; lustre highly metallic ; spe- cific gravity 11*370 at C., compared with water at 4 C. (Reich.) ; specific heat 0-03140 between 10 and 100 C., 0*03065 between 77*75 and 10 C. (Regnault), and 0-0402 be- tween 350 and 450 C. (Person) ; coefficient for linear dilation for 1 C. between and 100, 0-00003005 (Calvert and Johnson), for cubic dilation 0-000089 (Kopp). Its melting point is 326C.=619F. (Rudberg, Person); latent heat of fusion, 5*369 (Person). The conductivity of lead for heat and electricity is expressed by the numbers 8-5 for heat at 12 C., and 10 "7 for electricity, silver in both in- stances being 100 (Wiedermann). It crystal- lizes in octahedrons of the regular system. Lead is not sensibly volatile below a white heat if air be excluded, but even at this tem- perature it cannot be distilled like zinc. It is very soft, can be cut with a knife, and can be rolled or hammered into thin sheets. It is, however, but feebly ductile, and cannot be drawn into fine wire. Two clean and bright surfaces of lead may be united by simple pres- sure; tin and lead can also be united in the same way. The process seems to be one of true welding at ordinary temperatures, due to the softness of the metal. Finely divided metallic lead can also be united into a compact mass by pressure. When a pig of lead is heated near to its melting point, and then struck a sharp blow, it breaks like tin into a number of pieces having a remarkably colum- nar structure; the purer the lead the more columnar is the fracture. On bending cast or rolled lead no sound is emitted, as in the case of tin. When solidified and cooled slowly, lead is so soft that it can be indented with the finger nail; when melted at a high temper- ature and cooled suddenly, it is much harder.