resj')ecting the Ttmperalmc of Mines. 99 



*' In making a f'ev/ observations on the foregoing experi- 

 ments," Mr. Moyle continues, " I must remark, in the first 

 place that in mines wliich are at work scarcely two places of 

 equal depth below the surface, and under similar circum- 

 stances, exhibit the same temperature ; nor can I find, where 

 it increases with the depth, that there is any certain ratio ; it 

 being often, as in Oatfield, colder at 70 than at 4-0 fathoms 

 deep. As these differences and irregularities of temperature 

 always occur in mines which are at work, they must arise from 

 adventitious causes. I am therefore of opinion that the ti'ue 

 temperature of any part of a mine in the full course of work- 

 ing, is difficult of attainment, and that we must have recourse 

 to those mines, and parts of mines, which have been long smce 

 quitted by the miner, in order to obtain any thing like a true 

 datum." 



" Most of the deep mines now at work show an increase of 

 temperature of more than 1° for every 10 fathoms of descent; 

 at least it amounts to this on the whole, akhough its pro- 

 gressive ratio is not in that proportion : to show therefore that 

 this increase of heat arises from causes operating only in mines 

 at work, we have merely to refer to the temperature of mines 

 long since relinquislied, the highest -of which appears to be 

 56°, only 3° above the mean of this neighbourhood." 



" The experiments already mentioned clearly prove that 

 the water in relinquished mines exhibits nearly the same de- 

 gree of temperature at all depths ; and as it is demonstrated 

 that water is a bad conductor of caloric, except in an upward 

 direction, it is natural to infer that the temperature of the 

 deepest parts of those mines which are full of water, may be 

 ascertained by sinking the thermometer a few feet or fathoms 

 below the surface." 



" The water in the two shafts of Herland Mine indicated 

 different temperatures ; viz. 54° and 56°, and this difference 

 was the same at all depths. Now had the temperature of the 

 earth been uniform at the same depth, there woiild hiive been 

 no difference whatever*." 



" The temperature of die water at the deepest part of Huel 

 Alfred (130 fathoms) was only 56°; but according to the theory 

 of progressive heat, it ought to have been 66°." 



" The hot springs which frequently occur, whilst they pi'ove 

 the existence of causes sufficient to give them their high de- 

 gree of temperature, prove at tlie same time, by their rarity, 

 liie local and adventitious nature of those causes. Such springs 

 are sometimes met with at the very bottom of our mines, as at 

 Dolcoath." 



« The water issuing immediatelv from copper veins is ge- 

 N 2 " nerally 



