Page:De re metallica (1912).djvu/89

Rh entitled De Subterraneorum Ortu et Causis. It occasionally happens, though it is unusual and rare, that several accumulations of this kind are found in one place, each one or more fathoms in depth and four or five in main their origin was due to the combination of "dry things," such as "earth," with water, the mixture being heated, and the resultant metals depended upon the proportions of "earth" and water. In some cases we have been inclined to translate succus (juice) as "solution," but in other cases it embraced substances to which this would not apply, and we feared implying in the text a chemical understanding not warranted prior to the atomic theory. In order to distinguish between earths, (clays, etc.,) the Peripatetic "earth" (a pure element) and the earth (the globe) we have given the two former in quotation marks. There is no doubt some confusion between earth (clays, etc.) and the Peripatetic "earth," as the latter was a pure substance not found in its pristine form in nature; it is, however, difficult to distinguish between the two. (De Ortu, p. 35). I now come to the canales in the earth. These are veins, veinlets, and what are called ’seams in the rocks.’ These serve as vessels or receptacles for the material from which minerals (res fossiles) are formed. The term vena is most frequently given to what is contained in the canales, but likewise the same name is applied to the canales themselves. The term vein is borrowed from that used for animals, for just as their veins are distributed through all parts of the body, and just as by means of the veins blood is diffused from the liver throughout the whole body, so also the veins traverse the whole globe, and more particularly the mountainous districts; and water runs and flows through them. With regard to veinlets or stringers and ’seams in the rocks,’ which are the thinnest stringers, the following is the mode of their arrangement. Veins in the earth, just like the veins of an animal, have certain veinlets of their own, but in a contrary way. For the larger veins of animals pour blood into the veinlets, while in the earth the humours are usually poured from the veinlets into the larger veins, and rarely flow from the larger into the smaller ones. As for the seams in the rocks (commissurae saxorum) we consider that they are produced by two methods: by the first, which is peculiar to themselves, they are formed at the same time as the rocks, for the heat bakes the refractory material into stone and the non-refractory material similarly heated exhales its humours and is made into ’earth,’ generally friable. The other method is common also to veins and veinlets, when water is collected into one place it softens the rock by its liquid nature, and by its weight and pressure breaks and divides it. Now, if the rock is hard, it makes seams in the rocks and veinlets, and if it is not too hard it makes veins. However, if the rocks are not hard, seams and veinlets are created as well as veins. If these do not carry a very large quantity of water, or if they are pressed by a great volume of it, they soon discharge themselves into the nearest veins. The following appears to be the reason why some veinlets or stringers and veins are profundae and others dilatatae. The force of the water crushes and splits the brittle rocks; and when they are broken and split, it forces its way through them and passes on, at one time in a downward direction, making small and large venae profundae, at another time in a lateral direction, in which way venae dilatatae are formed. Now since in each class there are found some which are straight, some inclined, and some crooked, it should be explained that the water makes the vena profunda straight when it runs straight downward, inclined when it runs in an inclined direction; and that it makes a vena dilatata straight when it runs horizontally to the right or left, and in a similar way inclined when it runs in a sloping direction. Stringers and large veins of the profunda sort, extending for considerable lengths, become crooked from two causes. In one case when narrow veins are intersected by wide ones, then the latter bend or drag the former a little. In the other case, when the water runs against very hard rock, being unable to break through, it goes around the nearest way, and the stringers and veins are formed bent and crooked. This last is also the reason we sometimes see crooked small and large venae dilatatae, not unlike the gentle rise and fall of flowing water. Next, venae profundae are wide, either because of abundant water or because the rock is fragile. On the other hand, they are narrow, either because but little water flows and trickles through them, or because the rock is very hard. The venae dilatatae, too, for the same reasons, are either thin or thick. There are other differences, too, in stringers and veins, which I will explain in my work De Re Metallica. . . . There is also a third kind of vein which, as it cannot be described as a wide vena profunda, nor as a thick vena dilatata, we will call a vena cumulata. These are nothing else than places where some species of mineral is accumulated; sometimes exceeding in depth and also in length and breadth 600 feet; sometimes, or rather generally, not so deep nor so long, nor so wide. These are created when water has broken away the rock for such a length, breadth, and thickness, and has flung aside and ejected the stones and sand from the great cavern which is thus made; and afterward when the mouth is obstructed and closed up, the whole cavern is filled with material from which there is in time produced some one or more minerals. Now I have stated