other sand, and scattered far and wide in different directions, or they sink down into the depths of the sea. For the same reasons, the sands of lakes can very rarely be washed successfully, even though the streams rising from the mountains pour their whole volume of water into them. The particles of metals and gems from the springs are very rarely carried into the marshes, which are generally in level and open places. Therefore, the miner, in the first place, washes the sand of the spring, then of the stream which flows from it, then finally, that of the river into which the stream discharges. It is not worth the trouble to wash the sands of a large river which is on a level plain at a distance from the mountains. Where several springs carrying metals discharge their waters into one river, there is more hope of productive results from washing. The miner does not neglect even the sands of the streams in which excavated ores have been washed.
The waters of springs taste according to the juice they contain, and they differ greatly in this respect. There are six kinds of these tastes which the worker[1] especially observes and examines; there is the salty kind, which shows that salt may be obtained by evaporation; the nitrous, which indicates soda; the aluminous kind, which indicates alum; the vitrioline, which indicates vitriol; the sulphurous kind, which indicates sulphur; and as for the bituminous juice, out of which bitumen is melted down, the colour itself proclaims it to the worker who is evaporating it. The seawater however, is similar to that of salt springs, and may be drawn into low-lying pits, and, evaporated by the heat of the sun, changes of itself into salt; similarly the water of some salt-lakes turns to salt when dried by the heat of summer. Therefore an industrious and diligent man observes and makes use of these things and thus contributes something to the common welfare.
The strength of the sea condenses the liquid bitumen which flows into it from hidden springs, into amber and jet, as I have described already in my books "De Subterraneorum Ortu el Causis"[2]. The sea, with certain
- ↑ Excoctor,—literally, "Smelter" or "Metallurgist."
- ↑ This reference should be to the De Natura Fossilium (p. 230), although there is a short reference to the matter in De Ortu et Causis (p. 59). Agricola maintained that not only were jet and amber varieties of bitumen, but also coal and camphor and obsidian. As jet (gagates) is but a compact variety of coal, the ancient knowledge of this substance has more interest than would otherwise attach to the gem, especially as some materials described in this connection were no doubt coal. The Greeks often refer to a series of substances which burned, contained earth, and which no doubt comprised coal. Such substances are mentioned by Aristotle (De Mirabilibus. 33, 41, 125), Nicander (Theriaca. 37), and others, previous to the 2nd Century B.C., but the most ample description is that of Theophrastus (23-28): " Some of the more brittle stones there also are, which become as it were burning coals when put into a fire, and continue so a long time; of this kind are those about Bena, found in mines and washed down by the torrents, for they will take fire on burning coals being thrown on them, and will continue burning as long as anyone blows them; afterward they will deaden, and may after that be made to burn again. They are therefore of long continuance, but their smell is troublesome and disagreeable. That also which is called the spinus, is found in mines. This stone, cut in pieces and thrown together in a heap, exposed to the sun, burns; and that the more, if it be moistened or sprinkled with water (a pyritiferous shale?). But the Lipara stone empties itself, as it were, in burning, and becomes like the pumice, changing at once both its colour and density; for before burning it is black, smooth, and compact. This stone is found in the Pumices, separately in different places, as it were, in
