66 HISTORY OF 



to venture down to their deepest recesses ; and 

 some few who have tried, have been able to bring 

 back no tidings of the place, for unfortunately 

 they lost their lives below. The excavations of 

 art have conducted us much farther into the 

 bowels of the globe. Some mines in Hungary 

 are known to be a thousand yards perpendicularly 

 downwards ; and I have been informed, by good 

 authority, of a coal-mine in the north of England, 

 a hundred yards deeper still. 



It is beside OUT present purpose to inquire into 

 the peculiar construction and contrivance of 

 these, which more properly belongs to the history 

 of fossils. It will be sufficient to observe in this 

 place, that as we descend into the mines, the va- 

 rious layers of earth are seen as we have already 

 described them ; and in some of these are always 

 found the metals or minerals, for which the mine 

 has been dug. Thus frequently gold is found 

 dispersed and mixed with clay and gravel ; * 

 sometimes it is mixed with other metallic bodies, 

 stones or bitumens ; and sometimes t united with 

 that most obstinate of all substances, platina, from 

 which scarce any art can separate it. Silver is 

 sometimes found quite pure,t sometimes mixed 

 with other substances and minerals. Copper is 

 found in beds mixed with various substances, 

 marbles, sulphurs, and pyrites. Tin, the ore of 

 which is heavier than that of any other metal, is 

 generally found mixed with every kind of matter :, 



* Ulloa, vol. ii. p. 470. f Ulloa, ibid. 



\ Macq.uer's Chemistry, vol. i. p. 316. Hill's Fossils, p. 628, 



