294 



FORMATION OF VEINS. 



to contain any ore, and often entirely disappears : on sinking through 

 the loadstone to the second limestone, the ore is found again, but is 

 cut off by a lower bed of toadstone, under which it appears again in 

 the third limestone. In strong veins, panicles of lead occur in the 

 toadstone, but in very small quantities. 



If mineral veins were filled from above by metallic solutions, it is 

 impossible to conceive that the nature of the rock should change the 

 quality of the ore ; much less could the ore disappear in one stratum, 

 and appear again in a stratum below it. Nor could the vein be filled 

 with melted matter ejected from below; for in either case it would 

 be equally impossible, to explain why the ore disappears in the toad- 

 stone, though the vein is continued through it. See Plate IV. fig. 5, 

 where 6, 6, b are three beds of limestone divided by beds of loadstone 

 «e, and covered by sandstone. When the vein descends to the first 

 bed of toadstone e, the ore disappears ; but on sinking through to the 

 second bed of limestone, it is found again ; it disappears a second 

 time at the next bed of toadstone, and reappears in the lower lime- 

 stone, 3. Another vein, a or, is supposed to penetrate the beds of 

 toadstone e e, but contains little ore where it passes through them. 

 The upper part of the vein cr, is represented as penetrating the 

 superincumbent sandstone, which is sometimes the case : in this up- 

 per part of the vein, the most curious productions of the Odin mine, 

 near Casdeton, are discovered. Such facts prove that these veins 

 were not filled from above. Professor Jameson has conjectured that 

 the beds of toadstone and limestone in Derbyshire, with the metallic 

 veins, were all cotemporaneous, and that the toadstone crossed 

 through the veins, at the time of their formation ; but the different 

 organic remains in the upper and lower beds of limestone preclude 

 the possibility of their having been formed at the same time. The 

 zoophytes in the lower bed of rock could not be living and co-existent 

 with those in the upper, nor with the vegetable remains occasionally 

 found in the sandstone, which frequently covers the whole, and into 

 which the veins sometimes shoot. Cuvier has well observed, that 

 the existence of different organic remains offers incontestable proofs, 

 that the upper and lower strata in which they were found, were form- 

 -ed in succession. As a farther proof of the influence which the po- 

 sition of the rock has upon the vein which intersects it, the miners 

 both in Wales and Derbyshire maintain, that wherever there is a de- 

 pression in the strata, and they dip on both sides towards the vein, 

 (see Plate VII. fig. 9;) in such situations, the richest veins occur. 



If metallic matter were not poured in from above, nor ejected 

 from below, in what manner did it come into the vein ? The state, 

 of chemical science, and the facts at present known, are too limited 

 to furnish a solution to this interesting question. There are, how- 

 ever, certain indications which may serve as a clue to future discov- 

 ery. The variation of the mineral products in veins, as they pass 

 through different strata, seems to prove, that the strata were efficient 



