104' Summary Review of the late Invesfigatiotis 



He then examines what he considers to be the only important 

 instances of the above kind, which Dr. F. brings forward in sup- 

 port of his conchisions, viz. those of the collections of water in 

 the mines of Botallack and Little Bounds ; observing, with re- 

 spect to the first, that " the heat of this 'water at the bottom of the 

 iwrkhtg is not given ;" and asking, as to the second, the tempera- 

 ture of which. Dr. Forbes states, "as discharged by the pumps 

 in 1822, is 56\°" — " Pray what has this to do with the tem- 

 perature of the central part or bottom of the collection ?" — 

 *' And yet Di*. F.," continues Mr. M., " in nearly the following 

 page, states, that a large body of water resembling the last 

 has accumulated in the old wrought part of Ding-X)ong mine ; 

 at the depth of 444' feet below the surface, the v/orkmen had 

 just cut through the barrier v.hich divided them from this old 

 working, and the stream of water which issued forth (and 

 which was the bottom of the large collection) was only 52\, 

 thus at once proving what is actually the case, that, as I be- 

 fore stated, it may be as cold at tlie very centre of the earth 

 as at any distance beneath its surface." 



" In the next place, I do not conceive that their opinion 

 can be supported, because Dr. Forbes's philosophical rea- 

 soning on all the extraneous sources of caloric falls short of 

 what is actually observed, and that we must attribute this extra 

 portion as derived fi'om the earth itself; for I should imagine 

 that there are few more difficult problems, than a true estima- 

 tion of the power of the injinite sources of caloric in a mine in 

 the full course of working." — Anii. Phil. Jan. p. ST-^S. 



VI. Since the present article was prepared for the press, 

 the following " Notice in regard to the Temperature oj Mines" 

 by Mathew Miller, Esq. M.W.S. has appeared in the Me- 

 moirs of tlie Wernerian Natural History Society, vol. iv. 

 part ii. p. 466. 



" The late experiments on the temperature of mines made 

 in Cornwall, and in odier countries, having given rise to va- 

 rious speculations in regard to the distribution of heat in the 

 crust of the earth, all of which appear to me to be unsatisfac- 

 tory, I now beg leave to offer for consideration of the Society, 

 an explanation, that does not seem liable to the objections that 

 have been opposed to the others. 



" In every mine, with the exception of a few, which are 

 level-free, the ventilation is carried on by causing the air at the 

 surface to descend, ;ind traverse the works, and then ascend. 

 Now, it is evident, that if a portion of air from the surface be 

 carried down to tlie bottom of the mine, it will be condensed in 

 pi'oportion to the depth of the mine, and, in consequence of 

 this condensation, will become heated, and the degree of heat 



will 



