96 THE HISTORY OF 



CHAPTER VIII. 



OF MINES, DAMPS, AND MINERAL VAPOURS. 



THE caverns, which we have been describing, generally carry us but 

 a very little way below the surface of the earth. Two hundred feet, 

 at the utmost, is as much as the lowest of them is found to sink. The 

 perpendicular fissures run much deeper ; but few persons have been 

 iiold enough to venture down to their deepest recesses ; and some few 

 tttio have tried, have been able to bring back no tidings of the place, 

 fir unfortunately they left their lives below. The excavations of art 

 have conducted us much further 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 our present purpose to inquire into the peculiar con- 

 struction 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 various 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 fre- 

 quently gold is found dispersed and mixed with clay and gravel ;* some- 

 times it is mixed with other metallic bodies, stones, or bitumens ;t and 

 sometimes united with that most obstinate of all substances, platina, 

 from which scarce any art can separate it. Silver is sometimes found 

 quite pure,f sometimes mixed with other substances and minerals. 

 Copper is found in beds mixed with various substances, marbles, sul- 

 phurs, and pyrites. Tin, the ore of which is heavier than that of any 

 other metal, is generally found mixed with every kind of matter : lead 

 is also equally common ; and iron we well know can be extracted 

 from all the substances upon earth. 



The variety of substances which are thus found in the bowels of the 

 earth, in their native state, have a very different appearance from what 

 they are afterwards taught to assume by human industry. The rich- 

 est metals are very often less glittering and splendid than the most use- 

 less marcasites ; and the basest ores are in general the most beautiful 

 to the eye. 



This variety of substances, which compose the internal parts of our 

 globe, is productive of equal varieties, both above and below its sur- 

 face. The combination of the different minerals with each other, the 

 heats which arise from their mixture, the vapours they diffuse, the fires 

 which they generate, or the colds which they sometimes produce, are 

 ail either noxious or salutary to man ; so that in this great elaborato- 

 ry of nature, a thousand benefits and calamities are forging, of which 

 we are wholly unconscious ; and it is happy for us that we are so. 



Upon our descent into mines of considerable depth, the cold seems 

 to increase from the mouth as we descend ;|| but after passing very low 

 we begin by degrees to come into a warmer air, which sensibly 



Ulloa, vol. ii. p. 470. f Ulloa, ibid. } Macquer's Chymistry, vol. i. p. 316. 

 J Hill's Fossils, p. 623. || Boylej vol. iii. p. 232. 



