ON THE ORIGIN AND CAUSES OF SUBTERRANEAN THINGS, BOOK I

I will not speak of the hidden rumblings of murmuring water, which flows and roars under the earth, as is heard in some places, such as the Swedish mountains called Schula. Furthermore, there have been massive caverns—as we understand from the facts themselves—into which fields, cities, and mountains are said to have descended. Nor, indeed, do these small caverns catch only enough wind to be able to extrude and eject rocks of great weight into the air, or to upheave mounds, hills, and mountains, or to cause such great and terrible earthquakes that towns collapse. Puteoli was afflicted and fractured by this calamity and the subsequent fires last year. However, an internal fire of the earth can produce the concave depths of such caverns in the same way that water can, as I shall discuss later. The impetus of the water, when the channels through which it previously flowed are blocked or abandoned, immediately opens new ones or reopens old ones; and this order is preserved through the eternal ages of time. Channels are obstructed by silt or by collapse; they are abandoned when the force of the water has opened a path through some other channel. And let this suffice for what has now been said concerning the effects of subterranean waters.

But juices, which thickness (as I have said) distinguishes from waters, are produced in various ways. They are produced either when heat mixes a dry substance with a moist one and cooks them through the mixture; by this means, the vast majority of juices arise not only within the earth but also outside it. Or they are produced when waters licking the earth become somewhat thick, by which method, indeed, salt and bitter juices are generally formed. Or they are produced when a contained humor surrounds metallic matter, especially copper-bearing material, and corrodes it; and in this way, the juice from which chrysocolla gold-solder/mineral pigment is born is created. Similarly, when humor corrodes copper-bearing and friable pyriten pyrite, a sharp juice is formed, from which arises shoemaker's ink and, sometimes, liquid alum. Or finally, juices are squeezed out of the earth by the very power of heat. If that force is great, the juice oozes and flows from the earth, just as pitch does from burned pine trees; if the force is not great, as is the case with hot exhalations, the juices of the earth trickle like resin from the larch, fir, and trees of that same genus. It is in this way that we understand the kinds of bitumen to be formed in the earth. Just as various humors are produced in the bodies of living things, so the earth also produces waters endowed with diverse qualities, and likewise juices. They differ in touch, color, taste, odor, thickness, and weight. I shall now disclose the causes of these qualities.

Since water is by nature extremely cold, I have deemed it worth the effort to first investigate the causes of hot waters. Therefore, one of two things must be the case: either the heat of some other thing warms them, or fire itself does. If another thing warms the waters, it must be considered whether it is the sun, the wind, motion, internal earth heat, or finally the material through which the waters flow. First, those who judge that the sun’s rays warm the waters say that near hot springs the earth is soft and porous; and through that porosity...