There is a famous alum mine at Tolfa, near Civita Vecchia, in Italy. The alum is obtained from this mine nearly in a pure state; and it is so extremely hard, that it can only be wrought by means of pickaxes, and gunpowder. At Solfatara, near Naples, and in other volcanic countries, an abundance of alum is found, in a state of efflorescence, from the lava. The alum of our own country is manufactured from a kind of slaty stone which is found near Whitby, in Yorkshire. This manufactory was first established about the conclusion of the sixteenth century, by Sir Thomas Chaloner, who is supposed to have obtained his knowledge of the process, from the alum works which had then lately been introduced into Germany and Spain. The rock of _alum slate_, near Whitby, is supposed to be nearly twelve miles in extent: and affords an abundant supply of alum. The workmen tear open the rock; after which the different fragments are loosened, in the form of slaty leaves or plates, that are of a dark grey colour. To obtain the alum, a bed of fagots is formed from ten to twelve feet in depth. By the side of this a scaffold is erected, which enables the workmen to form a pile of mineral about fifty feet long, and forty feet high. While this pile is forming, the fagots are lighted. By the gradual operation of the heat, a calcination takes place, in consequence of which the alum is afterwards rendered capable of being more easily separated than it otherwise would be from the stone in which it was contained, and from other extraneous matters that are combined with it. After this, the mineral is washed in shallow vessels, so arranged that the water may be poured from one into the other. By this process the alum becomes suspended in the water, while all the earthy particles subside to the bottom. The next operation is to evaporate the water saturated with alum. This is done by boiling it in large leaden caldrons, fixed, on cast iron bars, over a furnace. As soon as the contents of the caldrons are brought to a proper state, they are drawn off into casks, where the alum concretes into a mass. The hoops are then taken off, and the alum is broken and left to dry; after which it is packed in casks for sale.