444 (hi the Temperature of Mines. [Dec. 



local and accidental causes which operate in our mines, and 

 aftect their temperature. The Hghted candles, and the blasting 

 of the rocks, have doubtless some influence in augmenting the 

 heat ; and the presence of the workmen must also have the same 

 tendency, although probably in a small degree at the bottom of 

 deep mines, where the temperature so nearly approaches to that 

 of tne human body ; moreover, the warm vapour, and air, which 

 always arise from the bottom of mines, must raise the tempera- 

 ture of the upper levels in a greater or less degree, accordinjj to 

 their relative situations. On the other hand, the currents of air 

 which descend through some of the shafts, or are forced through 

 the air-pipes for the supply of the miners, and likewise the 

 water which finds its way through the strata and veins from more 

 elevated situations, doubtless tend, in a considerable degree, to 

 diminish the heat in the deeper levels. 



How far these opposite causes may counterbalance each other, 

 it is not easy to ascertain ; but if duly considered, they will 

 gi'eatly reconcile the want of complete accordance in the results 

 noted in the tables ; and it is evident, that observations made 

 on the temperature at the bottom of mines, are most to be con- 

 fided in, not only for the foregoing reasons, but also because of 

 the proximity of this part to the unbroken ground. There are 

 some cases in which it cannot be supposed that the high temper- 

 ature observed can be occasioned by any accidental circum- 

 stance. At the bottom of Dolcoath mine, for instance, there is 

 a large stream of water issuing from one of the veins at 82° of 

 Fahr. while the air near the same place is generally one or two 

 degrees lower : — this is only one example amongst many of the 

 same kind. The most striking one I have heard of, was reported 

 to me by Capt. Hosken : — An accident having happened to a 

 steam engine at the United Mines, the water increased so much 

 as to fill the levels marked in the table 190 and 200 fathoms, 

 under the surface ; and thus it continued for two days. Imme- 

 diately after it had been pumped out, and before the miners had 

 begun to work in those levels, he ascertained the temperature of 

 the ground in the upper one to be 87-l°, and in the lower one to 

 be 88°. On renewing his observations some days after the men 

 had resumed their work in these places, the heat had rather 

 diminished than otherwise. 



It is worthy of notice, that the principal part of the work is 

 not always carried on in the deepest part of the mines : on the 

 contrary, there are often more workmen employed at twenty or 

 thirty fathoms above the lowest part, than in the deepest level. 

 If therefore the increase in the temperature were wholly the 

 effect of adventitious causes, that increase would be greatest 

 where those causes had their largest operation ; but the facts 

 which I have detailed in the table, prove that, however various 

 may be the operation of accidental circumstances in different 

 parts of the mmes, the temperature invariably inpreases with the 

 depth. 



