MISCELLANEOUS MINERAL SUBSTANCES USED IN THE INDUSTRIAL ARTS.
Alum—Alum Mines of Tolfa—Borax—The Suffioni in the Florentine Lagoons—China-clay—How formed?—Its Manufacture in Cornwall—Plumbago—Emery—Tripolite 458
The Subterranean World · The Wunder Library — complete classics, free to read, with narration.