Slate was known to exist in this country to a slight extent in colonial days. It was then used for gravestones, and to some extent for roofing and school purposes. But most of our supplies came from Wales. It is stated that a slate quarry was operated in Northampton County, Pa., as early as 1805. In 1826 James M. Porter and Samuel Taylor engaged in the business, obtaining their supplies from the Kittanninny Mountains. From this time the business developed rapidly, the village of Slateford being an outgrowth of it, and large rafts being employed to float the product down the Schuylkill to Philadelphia. By 1860 the industry had reached the capacity of 20,000 cases of slate, valued at $10 a case, annually. In 1839 quarries were opened in the Piscataquis River, forty miles north of Bangor, Me., but poor transportation facilities retarded the business. Vermont began to yield in 1852. New York's quarries are confined to Washington County, near the Vermont line. Maryland has a limited supply from Harford County. The Huron Mountains, north of Marquette, Mich., contain slate, which is also said to exist in Pike County, Ga. Grindstones, millstones, and whetstones are quarried in New York, Ohio, Michigan, Pennsylvania, and other States. Mica is found at Acworth and Grafton, N. H., and near Salt Lake, but our chief supply comes from Haywood, Yancey, Mitchell, and Macon counties, in North Carolina, and our product is so large that we can afford to export it. Other stones, such as silex, for making glass, etc., are found in profusion in various parts of the country, but we have no space to enter into a detailed account of them at present.--_Pottery and Glassware Reporter_. * * * * * AN INDUSTRIAL REVOLUTION.