n'sjjec/i/ig ilie Tcmpcrahoe of Mines. 



44-3 



All the artificial and extraneous sources of lieat in the mines 

 ofCornwall, Dr. Forbes observes, in the second part othis paper, 

 " are either the direct or indirect consequence of the presence 

 of the miner. Of the former class we have, — 1, animal heat; 

 2, combustion of candles ; 3, explosion of gunpowder ; 4, 

 friction and percussion: of the latter class, I shall have to no- 

 tice the effect of mining in lengthening the atmospheric co- 

 lumn." 



" In attempting to estimate th.e power of these causes, it will 

 be necessary to keep in mind the natui'e of the operations of 

 mining, and more especially the state of ventilation and mois- 

 ture, formerly described. It happens that almost all these 

 extraneous sources of heat exist in tlie very innermost extre- 

 mities of galleries which have only a very partial communicti- 

 tion with the shafts and more airy parts of the mine, and in 

 which, consc(]uently, there is very little change of the air. On 

 this account, and, moreover, because the v.alls of the galleries 

 arc not only very bad conductors of caloric, but arc absolutely 

 air-tight, the heat, from whatever cause arising, will be vciy 

 shnvly disjierscd. The water, also, as it oozes from the h de 

 in a state of extreme division, will seize and retain tlic heat, 

 and in many cases, no doubt, will convey it to the inferior <.al- 



» Here there was ;i stroiif: ctiiicnt of air. 



3 K 2 leries 



