SLAG 452 SLATTERY the Pyramids" (1909) ; "The Unholy Es- tate" (1912) ; "Germany's Great Lie" (1914); "Twenty Years of My Life" (1915) ; "Grace Lorraine" (1917) ; etc. SLAG, in metallurgy, vitreous mineral matter removed in the reduction of metals; the scoria from a smelting fur- nace. It is used for making cement and artificial stone, in the manufacture of alum and crown glass, and is cast into slabs for pavements, garden rollers, etc. In founding, the fused sullage and dross which accompany the metal in a furnace, and which it is the business of the skim- mer to hold back from the ingate. Also the scoria of a volcano. SLATE, a very remarkable form of clay rock, frequently fossiliferous and not confined to one geological period. Consisting essentially of clay, the par- ticles of slate are so mechanically ar- ranged that the rock splits with perfect facility into almost indefinitely thin layers in one direction only, and in all others either breaks with a jagged edge, or in well-defined joints at some distance from each other. Mineralogically slate is nothing more than a pure clay; nor does there seem any reason to suppose that any approach is made in it toward crys- talline structure. As, however, no other rock shows this tendency to split indefi- nitely, the case is one of great interest. Practically slate is very valuable, owing to its peculiar facility of splitting and the perfectly smooth natural face which it presents. Its hardness and compact- ness preserve it from all weathering by mere exposure, though, when ground down, it easily passes back into fine clay. Slate is always, and properly, regarded as a metamorphic rock. For a long time slate was used almost exclusively for roofing. For this purpose the slates are cut into sizes varying from a few square inches to two square feet, though some are much larger. This is done with very simple tools and extreme rapidity. The rest is in slabs or thick slates, often very large. The use of slate and slabs has increased considerably of late years. Slabs are now used in house fittings; as in strong rooms, powder magazines, lar- ders, partitions, baths, stables, floors, etc. It is very largely used also for enamel- ing; the surface of enameled slate being made to represent marble of all kinds with wonderful accuracy, and resisting almost all wear. Quarries of great mag- nitude are worked in Cornwall, Wales, Scotland, and Ireland. The product of the Welsh quarries was formerly largely exported to the United States, but this business received a serious check on the opening of valuable quarries in Vermont, New York, Pennsylvania, Maryland, and other states. Adhesive slat<j is a kind of greenish- gray slate, quickly absorbent of water, and remarkable for its adhesiveness. Bi- tuminous slate, a soft species of sectile slate clay impregnated with bitumen; hornblende slate, a slaty rock consisting of hornblende and feldspar with some chlorite, principally used for flagging pavements, etc. SLATIN PASHA (Baron Rudolf Carl), an Austrian soldier, born near Vienna, in 1857. After service in the Austrian Army, he engaged in service in Egypt under General Gordon, and in 1881 was made Governor-General of Dar- fur. Shortly after, the Mahdi aroused his followers and began the famous re- ligious war which resulted in 1884 in the defeat of Hicks Pasha, and the capture of Slatin by the Mahdists. He was made practically a slave of the Mahdist com- mander, Abdullahi, who succeeded the Mahdi after the latter's death. He was kept in captivity for 11 years, until 1895, when he succeeded in escaping to Lower Egypt. He was made a pasha by the Khedive, and was appointed in 1900 British Inspector-General of the Sudan. In 1906 he was created a Baron of the Austrian empire. He had already been made an honorary major-general in the British army, but in 1914 renounced this and other British honors. SLATTERY, CHARLES LEWIS, an American Protestant Episcopal clergy- man, born in Pittsburgh, Pa., in 1867. He was educated at Harvard and the Epis- copal Theological School, Cambridge, Mass. He was made a deacon in 1894, and a priest in 1895. From 1894 to 1896 he was rector of St. Andrew's, Ayer, Mass., and a master at Groton School from 1896 to 1907 dean of the Cathedral at Faribault, Minn.; from 1907 to 1910 rector of Christ Church, Springfield, Mass., and since May, 1910, rector of Grace Church, New York City. He was at various times a lecturer at Seabury Divinity School, Faribault, Minn., and at Berkeley Divinity School, as well as paddock lecturer at the General Theo- logical Seminary (1911-1912) ; and West lecturer at Stanford University (1915). He wrote: "Felix Reville Brunot" (1901) ; "Edward Lincoln Atkinson" (1904) ; "The Master of the World— a Study of Christ" (1906); "Life Beyond Life— a Study of Immortality" (1907) ; "The Historic Ministry and the Present Christ" (1908) ; "Present-Day Preaching" (1909) ; "Alex- ander Viets Griswold Allen" (1911) ; "The Authority of Religious Experience" (1912); "The Light Within" (1915);
