GEOLOGY. 155 



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 addi- 

 tional 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 oxygen- 

 ized metals, or as they are called mineral spars, as spathic- 

 iron, malachite, calamine, lead-spar, pyrornorphite, &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 de- 

 creased 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 princi- 

 ples 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 



