76 Featherstonhaugh's Geological Report. 



the cultivation of geological knowledge that has led to so much 

 minute investigation of the nature of veins, and to that proper 

 degree of chemical information which has redeemed the 

 mining interest from the rude management of the common 

 miner, and introduced those truly economical practices which 

 are only united by science and experience. 



An opinion once obtained that below a given depth the 

 veins ceased to be productive ; tin from twenty to sixty fathoms 

 was supposed to be most abundant, and copper from forty to 

 fifty. This has become a speculation of some importance to 

 the gold mining interest here, some of the mines having been 

 abandoned because the veins seemed to fail even at twenty 

 fathoms. Of late, the mines in Cornwall have been worked 

 at very great depths, with the best results. Being a few years 

 ago in the Botalloch mine, in that country, I found them work- 

 ing in a. copper vein at the depth of 950 feet, which I was in- 

 formed was the best ore they had yet met with. Others, such 

 as the consolidated mines, are worked in England at a depth 

 of more than 1,600 feet; and one of the continental mines, 

 the Kits Piihl copper mine, in Tyrol, at a depth of near 2,800 

 feet. Reasoning from analogy, it would seem a hasty pro- 

 ceeding, after expending a capital in mining machinery, to 

 abandon before a depth of at least 500 feet had been in- 

 vestigated. If the mineralogical structure of the mines was 

 totally different from that of the older mines, there would be 

 greater grounds for apprehension, working in the face of an 

 unknown state of things, but the analogical structure of the 

 metalliferous rocks in both hemispheres holds out every en- 

 couragement to the mining interest in this : the veins are 

 found in the same kind of rocks, and have nearly the same 

 magnetic direction. In the gold countries the mass of the 

 veins is usually quartz, bearing visible native gold, and asso- 

 ciated with iron, as well as gold in a mineralized state with that 

 and the quartz when invisible. In the gold region of the 

 United States, these veins are easily distinguished, consisting 



