There are many species of earths which can be used by artisans for various purposes. I have described these earths, as I know them, in the previous book. I shall now take up the next class of minerals, congealed juices, of which, as I have said, there are four genera. The first embraces halite and nitrum; the second, alum, atramentum sutorium, and related minerals as well as the acrid juices; the third, sulphur, bitumen, realgar, and orpiment; the fourth, chrysocolla, aerugo, caeruleum, ferrugo, etc. I shall discuss each species in these four genera beginning with halite.
Sal (halite, salt) is known as both a natural mineral and an artificial product. Halite produced by Nature is found both within the earth and on its surface. When it occurs within the earth it is either quarried out of the mountains, or mined from beneath the fields or sands that cover it. The latter are stripped off before the mineral is recovered. There are many famous mountains of halite in the world. In Germany there is a salt lake just to the north of Seburg and rock salt occurs near the gateway of the Caspian Sea. It is not quarried at either place since, at the former locality, a river flows from the lake and carries particles of halite with it and in the latter region salt pits are common. From these the salt workers draw off liquid so rich that they have no need for the natural mineral. Halite is mined in . . .