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XVII. On the alleged Production of Heat in Mines ly the Con- 

 densation of the Air 'which ventilates them; and on the Fallacy 

 of other Objections to the Opinion that a high Temperature 

 exists in the Interior of the Globe. By RoBEnxW. Fox. 



To the Editors of the Philosophical Magazine and Annals. 



Gentlemen, 



A PAPER has recently appeared in the Edinburgh Re- 

 ** view* " On the Progress of Geological Science," in which 

 arguments are adduced against the existence of an elevated 

 temperature in the interior of the earth. 



These arguments are founded on the cold which prevails 

 about the poles, notwithstanding they are twelve miles nearer 

 the centre than the surface of the earth is at the equator ; and 

 on the comparatively low temperature of the water in aban- 

 donded mines, as well as at the bottom of the sea, as far as 

 this has been ascertained. 



It is at the same time admitted that the heat is found to in- 

 crease in mines in proportion as they are deepened, and that 

 its degree depends on their depth under the surface, rather 

 than with respect to the level of the sea. That it is not pro- 

 duced by the miners, and the candles and gunpowder they 

 use, is fully acknowledged, as the influence of those causes 

 must be perfectly insignificant on the large quantity of water 

 pumped out of deep mines. 



But the reviewers attribute the elevation of temperature 

 observed in mines to the condensation of the currents of air 

 which ventilate them. " Now," they say, " as this air passes 

 from the surface to the bottom of the minef, it becomes 

 more and more compressed. Its temperature in consequence 

 must be continually increasing, and of course it must be al- 

 ways giving out heat to the walls of the mine and to the water 

 with which it comes in contact. The heat given out at the 

 bottom will be greatest, because there the compression is 

 greatest. The greater the quantity of air thus condensed, 

 and the more rapid the current, the greater will be the quan- 

 tity of heat evolved. This, we are persuaded, is the true 

 cause of the elevation of temperature as a mine increases in 

 depth." 



These opinions, proceeding from such authority, induce 

 me, from the part I have taken in this question, and the op- 

 portunities I possess, from my local situation, for getting in- 

 formation relative to the Cornish mines, to offer a few remarks 



# Edinburgh Review, No. 103, p. 4952. 



f Dolcoath is the mine referred to, and 84 the temperature of the 

 water at the bottom, the mine being 238 fathoms deep. 



for 



