456 Proceedings of Philosophical Societies. [Dec. 



at first sight circumstances very startling to our preconceived 

 notions, and still more so vv^hen traced to the conclusions to 

 which they necessarily lead ; the author of the memoir, previously 

 to coming to any opinion as to the site or source of this high 

 temperature, discussed the many hypothetical objections that 

 can be advanced against the existence of an internalsourceof heat 

 in the body of the earth. We have not space to notice all these, 

 nor to notice any of them fully. The following, among others, 

 were particularly adduced and insisted on : 1. The fact that the 

 degree of elevation above the sea does not affect the temperature 

 of mines ; mountain mines, at equal depths below the surface 

 being as warm as those at the sea level. 2. The difference of 

 temperature in mines of the same depth under the surface. 



3. If so high a temperature existed at so comparatively small 

 depths, ought not the law of the equilibrium of caloric to render 

 this perceptible at the venj surface of the earth ? Ought not the 

 temperature of our deep wells and copious springs to be the mean 

 ootids internal temperature, and the external or atynospheric tem- 

 perature conjoined, and not of the latter only, as is the fact? 



4. Besides noticing the fact of the very low temperature of deep 

 seas and lakes, as bearing on the same point, Dr. Forbes brought 

 proofs that the temperature of several abandoned mines filled 

 with water for years, to the depth, at least, of several hundred 

 feet, is not greater than the mean temperature of Cornwall. 

 These and many other considerations naturally led the author to 

 inquire into the various possible sources of extraneous tempera- 

 ture that are found in mines, and to the examination of how far 

 these will go in accounting for their high temperature ; an. 

 inquiry, moreover, rendered more natural and necessary by the 

 fact, fully proved by the author of the memoir, of the presence or 

 absence of miners occasioning a difference often of 6, 8, or 10 

 degrees of temperature, in the same mine, or in different mines, 

 similarly circumstanced in other respects. The various sources 

 of extraneous temperature, noticed by Dr. Forbes, were : 

 1. Candles; 2. Gunpowder; 3. Friction and percussion ; 4. The 

 bodies of the miners ; 5. The diminished capacity of air for 

 caloric in deep mines, in consequence of the condensation caused 

 by the increased height of the atmospheric column. In estimat- 

 ing the effect of the four first sources, the author entered into 

 minute calculations, founded on the experiments of various phi- 

 losophers, and illustrated the whole by application to the case of 

 a single mine. The mine chosen for this purpose was the mag- 

 nificent copper mine of Dolcoath, which employs (underground) 

 750 persons, consumes monthly 3000 lbs. of gunpowder, and 

 5000 lbs. of candles ; is 1400 feet deep, and contains within it 

 upwards of 7,000,000 of cubic feet of excavated space. 



By Dr. F.'s calculations, it appeared probable that a quantity 

 of air might be heated daily in Dolcoath by the various extra- 

 neous causes mentioned, from the temperature of 52" to 60° 



