260 Mr. Moyle on the Temperature of Mines. [April, 



rose to 70°, while the air at the bottom of the winze was 72°. 

 I fastened a hue to the thermometer, and allowed it to remain 

 in the hole. The place was now relinquished, and was in the 

 course of a few hours full with water, and great care was taken 

 to prevent any of the water in common to the mine from running 

 into this reservoir. On the following day this water was found 

 at the surface 70°, at two fathoms in depth 68°, and at the bottom 

 67°; at the expiration of nearly three months, it was thought ne- 

 cessary to examine it again, as the approach of the end of the 120 

 fathom level might otherwise destroy the opportunity sought. 

 The water was now found at all depths to be 64°. A few weeks 

 after this, the water was found to be sinking, when additional 

 care was taken to prevent any water from falling into the winze; 

 when it had sunk to within tv^'o feet of the bottom, the thermo- 

 meter which was allowed to remain in the hole was suddenly 

 withdrawn, when it was found to be at 54°. Two days after this 

 period, this hole was dry, and showed the temperature of 70°. 



Not willing to rely too much on this single experiment, I 

 sought another opportunity of repeating it in Huel Vor tin mine, 

 situated in slate. Here a winze similarly circumstanced to the 

 one just related occurred at the 124 fathom level. This winze 

 was sunk just six fathoms before relinquished, at which time the 

 temperature was 75" ; but after being filled with water for about 

 two months, the registering thermometer indicated only 56° ; 

 and this possibly might be influenced in some measure by its 

 being found impossible wholly to exclude a fall of water run- 

 ning into it from above. 



1 do flatter myself that these experiments tend much to 

 strengthen my former assertions of the earth in general possess- 

 ing and preserving the mean annual temperature of the latitude ; 

 and although these experiments give a degree or two above this 

 mark, we cannot but suppose the local causes of heat in a mine 

 at full work must tend to influence the results ; but it should be 

 observed that it falls far below what we are taught to expect at 

 these depths, by those holding a ditt'erent opinion from myself. 



Should you, or any of your correspondents, who feel an interest 

 in the present question, be able to suggest any better plans than 

 those already adopted, I shall be most ready to second their 

 views, and will, as far as in my power, carry their intimations 

 into eft'ect. I am. Gentlemen, vour obedient servant, 



M. P. Moyle. 



