736. In the deeply situated veins, therefore, the more identical or purer formations of ore must occur; while, on the contrary, in those situated higher up or exposed to the day, i. e. in closer proximity to the water, air and light, the more different or compound formations of ore must be produced. 737. The four classes of ores occupy a position in the veins tolerably accordant with these relations; an additional proof that they have originated in the vein and not been floated into it by the action of water. 738. The production of ore which occurs in the _upper_ parts of the veins, furnishes us with the saline ores; for here the water, air and earth are principally active. In the upper depths are found most frequently the oxygenized metals, or as they are called mineral spars, as spathic-iron, malachite, calamine, lead-spar, pyromorphite, &c. Finally, the metallic or ore-spars actually pass over into salts, and by the horn-silver ores into the vitriols. They are for the most part crystallized. 739. The salt-formation of the ores has always decreased in proportion to the light having less access to it, and hence in greater depths, or in wholly mountainous masses. There the ore has not been deposited as a light-difference, but only as a Terrestrial, just as the earths, especially the calcareous earth, have obtained the same. It has not attained to a complete evolution of the polar body so as to constitute an acid, but the two principles have only emerged opposite to each other. They are oxydized ores, consequently those among the ores, that represent the character of earths, namely, the ochres. They are frequently uncrystallized. 740. So far the appearance of these ores is thoroughly earthy and devoid for the most part of metallic lustre; finally, the genesis of the ore turns upon the side of the identity, the principle of gravity having secured itself wholly in the depths, previous to the adverse accession of water and light. In such situations nothing more than heat and the centro-peripheric polarity of the vein-wall operates. The Metallic recedes wholly from the salt and from the earth. The oxygen disappears, but in its place comes sulphur, and the sulphuretted ores originate, e. g. the bi-sulphurets of iron, blendes, glance-ores. 741. Lastly, every combination or influence of the other elements and mineral-classes vanishes; acids, oxygen and sulphur are no longer generated in the perfectly dark depths, and the ore stands there in its entire identity, homogeneous, resplendent and heavy as the sterling metal. The same results from sublimation. The heavier metals remain below, the lighter ones and the sulphur ascend. 742. As the orders of earth are placed in the veins, so also are the different metals themselves; for the cause of genesis is alike in both.