Slate
a very remarkable form of clay rock, frequently fossiliferous and not confined to one geological period.
Consisting essentially of clay, the particles of slate are so mechanically arranged 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 crystalline structure. As, however, no other rock shows this tendency to split indefinitely, 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 compactness 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, larders, partitions, baths, stables, floors, etc. It is very largely used also for enameling; the surface of enameled slate being made to represent marble of all kinds with wonderful accuracy, and resisting almost all wear. Quarries of great magnitude 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, SLATTERY New York, Pennsylvania, Maryland, and other states.
Adhesive slate is a kind of greenishgray slate, quickly absorbent of water, and remarkable for its adhesiveness. Bituminous 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 Darfur. Shortly after, the Mahdi aroused his followers and began the famous religious 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 commander, 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.