1824.] Mr. Moyle on the Temperature of Mines. 447 



which we are acquainted, but that of evaporating, can by any pos- 

 sible chance controul the first. Hence it' a low temperature is met 

 with, it would seem to be a. more true criterion of the actual 

 state of the earth generally than we could possibly infer from 

 occasional instances of high temperature, because, were the 

 internal strata of the earth augmented in temperature according 

 to the descent, the emanation of whose caloric is said to be 

 sensible in our mines, a low degree of heat could in no one 

 instance occur. The act of boring holes in the solid rock at the 

 bottom of the mine, or in any other situation, to observe the 

 temperature, must be fallacious ; unless the hole is bored to a 

 considerable depth, and in the course of the lode, so that a body 

 of water shall issue in a full and powerful stream through it. The 

 heated air of the spot must penetrate, and the sides and bottom 

 of the hole soon acquire the same temperature as the external 

 walls of the gallery itself. This circumstance I have so often 

 proved, that I have always omitted the results as being deceit- 

 ful. The only way in which this experiment can succeed, so as 

 to supply a true data appears to be in the manner just stated, 

 with the proviso that the end of an extensive gallery, or some 

 other situation, is chosen the most remote from any working 

 part, and far beyond the perpendicular from the galleries which 

 lie above it as at A. B the perpendicular shaft, c c c c are 

 various galleries. 



J3 



JL 



I E 



31 



TT 



Novvif a hole is bored horizontally at A, on the course of the 

 lode, and so as to allow a full stream of water to pass through it, 

 it will be less liable to be influenced by the percolation of the 

 water from the galleries above it ; whereas should it be done in 

 any part at D, and there should exist a solid barrier of earth 

 from that place to the gallery above it, the water which 

 lodges at the bottom of the superincumbent gallery generally 

 finds its way perpendicularly to D, and consequently must bring 

 with it a medium temperature of what it possessed before, and 

 that of the stratum of earth through which it has passed, while 

 the water at A most probably will be free from all these objec- 

 tions. 



Bearing in mind these circumstances, I shall proceed to detail 

 a few experiments which I performed in the course of the last 



