1822.] Temperature of Mine$ in Cornwall, 309- 



descent, it appears that the temperature of the earth gradually 

 increased from that of 50* 18° Fahr. tit 10 fathoms to that of 

 82-04° Fahr. at 240 fathoms, the bottom of Dolcoath Mine. 

 This statement of Mr. Fox differing so entirely from a few obser- 

 vations which I made a few years since on the temperature of 

 mines, compels me to notice them, and more particularly when 

 Mr. F. would wish to infer the great superiority of temperature 

 of the internal part of the earth over that of the surface. At 

 the bottom of the mine at Dolcoath, 240 fathoms deep, ther^, 

 issues from the vein a jet of water, whose constant temperature 

 is 80-04° Fahr. " What more evident proof can be given," 

 says Mr. Fox, '^ of the great heat of the interior state of the 

 globe?" Surely Mr. F. would not infer from this the superior 

 neat of the internal strata generally ; he might as well draw his 

 conclusions from measuring the temperature of the boiling 

 fountain in Iceland, which spouts its columns to the height of 90 

 feet, and is found boiling-hot after its descent. The source of 

 this heat it is not necessary to discuss ; but I am apprehensive ' 

 that Mr. F. would not have found the temperature of the earth 

 at the same depth, and some way distant from the spring, sa 

 high. 



1 have taken the temperature of several different mines at 

 various depths, and in the working part of mines have generally 

 found the increase of temperature in a similar ratio to what Mr. 

 Fox states ; the cause of which 1 inferred was from the presence 

 of so numerous a body of workmen in different parts of the said 

 mine, often amounting to 400 or more, at one time, under ground, 

 and generally the greatest number at the bottom; also from 

 the greater confinement and density of the air. Surely this 

 must have a great effect in not only warming the atmosphere of 

 the spot, but the very walls of the galleries, and even their beds, 

 to the depth of many inches ; and although Mr. F. may have 

 taken his observations when the bulb of the thermometer ha§ 

 been " placed six or eight inches in the body of the rock," he 

 must not forget that the surrounding atmosphere must have 

 penetrated to that depth before he could possibly have placed 

 the thermometer there. 



I come now to state a few of the results of my own observa- 

 tions. It does not appear from Mr. Fox's account that any part 

 of a mine remote from the working had been proved, where we 

 certainly should expect to find the medium, or rather the true 

 mean, if any where. This I have done in several instances : one 

 or two may suffice to convince the candid reader that Mr. Fox 

 must either have drawn false conclusions, or did not take the 

 temperatures in a proper manner. 



Some years since in Wheal Unity (the same mine which Mr. 

 Fox visited), one of the galleries to the western part of the mine, 

 at the depth of about 150 fathoms, which had not been worked 

 fgr more than 12 months, at the extreme end, there being ngi^ 



