Page:De re metallica (1912).djvu/90

48 width, and one is distant from another two, three, or more fathoms. When the excavation of these accumulations begins, they at first appear in the shape of a disc; then they open out wider; finally from each of such

when discoursing on the origin of subterranean humours, that water erodes away substances inside the earth, just as it does those on the surface, and least of all does it shun minerals; for which reason we may daily see veinlets and veins sometimes filled with all’and water, but void and empty of mining products, and sometimes full of these same materials. Even those which are empty of minerals become finally obstructed, and when the rock is broken through at some other point the water gushes out. It is certain that old springs are closed up in some way and new ones opened in others. In the same manner, but much more easily and quickly than in the solid rock, water produces stringers and veins in surface material, whether it be in plains, hills, or mountains. Of this kind are the stringers in the banks of rivers which produce gold, and the veins which produce peculiar earth. So in this manner in the earth are made canales which bear minerals." . (De Ortu p. 5). .... Besides rain there is another kind of water by which the interior of the earth is soaked, so that being heated it can continually give off halitus, from which arises a great and abundant force of waters." In description of the modus operandi of halitum, he says (p. 6):. . . . Halitus rises to the upper parts of the canales, where the congealing cold turns it into water, which by its gravity and weight again runs down to the lowest parts and increases the flow of water if there is any. If any finds its way through a canales dilatata the same thing happens, but it is carried a long way from its place of origin. The first phase of distillation teaches us how this water is produced, for when that which is put into the ampulla is warmed it evaporates (expirare), and this halitus rising into the operculum is converted by cold into water, which drips through the spout. In this way water is being continually created underground." (De Ortu, p. 7): And so we know from all this that of the waters which are under the earth, some are collected from rain, some arise from halitus (steam), some from river-water, some from sea-water; and we know that the halitum is produced within the earth partly from rain-water, partly from river-water, and partly from sea-water." It would require too much space to set out Agricola’s views upon the origin of the subterranean heat which produced this steam. It is an involved theory embracing clashing winds, burning bitumen, coal, etc., and is fully set out in the latter part of Book II, De Ortu et Causis. . It is necessary to bear in mind that Agricola divided minerals (res fossiles Things dug up, " see note 4, p. i) into earths," solidified juices, " stones," metals, " and compounds; and, further, to bear in mind that in his conception of the origin of things generally, he was a disciple of the Peripatetic logic of a material substance and an efficient force, " as mentioned above.

As to the origin of earths," he says (De Ortu, p. 38): Pure and simple-’earth’ originates in the canales in the following way: rain water, which is absorbed by the surface of the earth, first of all penetrates and passes into the inner parts of the earth and mixes with it; next, it is collected from all sides into stringers and veins, where it, and sometimes water of other origin, erodes the ’earth’ away, a great quantity of it if the stringers and veins are in ’earth,’ a small quantity if they are in rock. The softer the rock is, the more the water wears away particles by its continual movement. To this class of rock belongs limestone, from which we see chalk, clay, and marl, and other unctuous ’earths’ made; also sandstone, from which are made those barren ’earths’ which we may see in ravines and on bare rocks. For the rain softens limestone or sandstone and carries particles away with it, and the sediment collects together and forms mud, which afterward solidifies into some kind of ’earth.’ In a similar way under the ground the power of water softens the rock and dissolves the coarser fragments of stone. This is clearly shown by the following circumstance, that frequently the powder of rock or marble is found in a soft state and as if partly dissolved. Now, the water carries this mixture into the course of some underground canalis, or dragging it into narrow places, filters away. And in each case the water flows away and a pure and uniform material is left from which ’earth’ is made. . . . Particles of rock, however, are only by force of long time so softened by water as to become similar to particles of ’earth.’ It is possible to see ’earth’ being made in this way in underground canales in the earth, when drifts or tunnels are driven into the mountains, or when shafts are sunk, for then the canales are laid bare; also it can be seen above ground in ravines, as I have said, or otherwise disclosed. For in both cases it is clear to the eye that they are made out of the ’earth’ or rocks, which are often of the same colour. And in just the same way they are made in the springs which the veins discharge. Since all those things which we see with our eyes and which are perceived with our senses, are more clearly understood than if they were learnt by means of reasoning, we deem it sufficient to explain by this argument our view of the origin of ’earth.’ In the manner which I have described, ’earths’ originate in veins and veinlets, seams in the rocks, springs, ravines, and other openings, therefore all ’earths’ are made in this way.