rocks, or at least certain kinds of them, can be made into wool. The wool is made from sandstone, and from the waste slag of furnaces. “Mineral wool” is already being used for packing and fireproofing; but the inexhaustible field for the industry in the millions of tons of serviceable rocks, and the unforeseen possibilities in the use of the “new wool,” make the subject a startling one and well worth the consideration of money-makers.