383 Mj\ Fox^s Remarks on Mr, Moyle*s Observations [May 



are to be inserted, is now in the press, I shall at present refrain 

 from entering into a detail of the facts which they contain, 

 must, however, observe, that my conclusions have been drawn 

 not only from the temperature of the veins, but from that of 

 cross levels at a considerable distance from them, and of those 

 parts of the mines which were least affected by currents of air, 

 and in which there were few or no workmen ; and although I 

 am well aware that many adventitious, and indeed opposite, 

 causes operate in mines, which render it difficult to obtain satis- 

 factory data as to the true temperature of the earth at equal 

 depths, I think it will appear, when the above-mentioned volume 

 is published, that due precautions have not been neglected to 

 prevent their effects as much as seemed practicable. 



The temperature at different depths and stations in 13 mines, 

 which varied from 540 to 1430 feet in depth, and averaged above 

 800 feet (being all those from which I have received any infor- 

 mation) is given in the communications to which I have referred ; 

 and not one instance has occurred in the course of my inquiries in 

 which the temperature was not greater in the deepest part of the 

 mine than near the surface ; and in most cases, it increased in 

 proportion to the depth. This remark applies whether the tem- 

 perature of the air, of the solid ground, or of the jets of water, as 

 they flowed into the mine, were taken ; yet commonly, a very 

 small proportion of the workmen in deep mines are employed in 

 the lowest galleries. 



I think the following facts are sufficient to prove, that the heat, 

 in some mines at least, must be attributed to some other cause 

 than the presence of the workmen, &:c. An opportunity occurred 

 some time ago at Treskerby Mine, which is 840 feet deep, to 

 ascertain the temperature after the workmen had been absent 

 for two successive days ; when it was found that no diminution 

 of heat had taken place during that time ; but that both the 

 "water (which flowed copiously into the bottom of the mine) and 

 the air continued at 76°. 



At the end of .the deepest gallery in Dolcoath Mine, 230 

 fathoms, or 1380 feet, under the surface, a thermometer four feet 

 long was inserted to the depth of three feet in the ground, and 

 was closed round with earth. In this situation, it was left more 

 than eight months, during which time no workmen were 

 employed near it ; it was frequently examined, and it denoted a 

 constant temperature of 75 or 75^°, except when the water 

 from accidents to the machinery gained on the pumps, and filled 

 the gallery, which occurred more than once for some weeks 

 together. Immediately after the water had been drawn out, the 

 mercury was found to have risen to 76° or 77° ; but in a few 

 days, it resumed its previous station of 75^°. 



An increase of temperature was also produced in the United 

 Mines in the two deepest galleries, 1140 and 1200 feet under 

 the surface, in consequence of an influx of water for a few days ; 



