1820.] Royal Geological Society of Cornwall, 457 



(which was considered the mean temperature of all the air 

 contained in the mine) sufficient to fill it thrice, or about 

 21,000,000 of cubic feet. Applied to watei; the same quan- 

 tity of caloric vvill raise from the temperature of 52° to 77° (the 

 mean temperature of the water in the mine) only 2,300 cubic feet 

 per day ; but the pumps of Dolcoath brin^ up daily upwards of 

 120,000 cubic feet of water of this temperature ! From this, 

 therefore, it is evident that the extraneous sources of caloric in 

 mines, although very important and more considerable than has 

 usually been allowed, entirely fail in accounting for the tempera- 

 ture found in them. An additional and hitherto unnoticed 

 source of increased temperature in mines is that arising from the 

 elongation of the atmospheric column, and consequent conden- 

 sation of the air — a cause constantly operating in every mine 

 where there is a circulation of the contained atmospheric fluid, 

 as is indeed the case in all mines. But this, even in the deepest 

 mines in Cornwall, will only cause an increase of four degrees ; 

 which, even when added to the other adventitious causes, 

 entirely fails to meet the degree of the actual temperature. In 

 the mines of Cornwall no decomposition of pyrites, or other 

 mineral matter, seeras to take place in any degree sufficient to 

 cause any perceptible augmentation of caloric. Whence, then, 

 we may ask with Dr. Forbes, is derived the high temperature of 

 mines ? Notwithstanding the strong arguments that can be 

 adduced against it, must we admit the existence of a constant 

 and natural temperature of from 70° to 80° in the body of the 

 earth at the depth of httle more than a thousand feet 1 Or are 

 there other adventitious causes, not yet suspected, that can ex- 

 plain this very striking and singular phenomenon ? Dr. Forbes 

 considered the mean temperature of the whole atmosphere at the 

 surface of the earth to be about QQ° of Fahrenheit, and stated 

 that tliis is the temperature which he would have expected, 

 a piiori, to be found on the earth at very great depths, that is, 

 on the supposition that there is no internal source of heat. He 

 concluded by promising some communication on the health 

 of miners as affiscted by the tropical temperature of their subter- 

 ranean climate. 



2. Another paper on the same subject by Mr. R. W. Fox, of 

 Falmouth, was also read, being the second on this interesting 

 topic presented by this gentleman to the Society. Mr. Fox's 

 paper was chiefly occupied in detailing ol)servations on the tem- 

 perature made in upwards of ten mines, and exhibited the results 

 in tables. From these Mr. Fox drew the conclusion that the 

 temperature of the earth in Cornwall progressively increases as 

 we descend, nearly in the ratio of one degree of Fahrenheit for 

 60 or 70 feet. Mr. Fox has an idea that the ascent of vapour 

 through the lodes, and its condensation in the mine, may be aa 

 important agent in the production of heat in these recesses. A. 

 very singular fact was detailed in this paper. An accident hav-- 



