96 Mr. R. W. Fox on the Increase of Heat in Mines, 



it is clear that the air which circulates in mines tends to di- 

 minish, and not to augment their temperature. The air sup- 

 plied by mechanical means is comparatively trifling; this mode 

 of ventilation being resorted to only, when, from a deficiency 

 of shafts, the circulation is very imperfect; and as it must ul- 

 timately form a part of the warm ascending currents, it is un- 

 necessary to consider its effect on temperature as a distinct 

 question. 



True it is, that the ratio of increase is by no means uniform 

 in the mines ; nor ought it to be expected to be so, as there 

 are many disturbing causes which must affect the temperature 

 very differently in different places. Of these, the copious fil- 

 tration of water into the deepest excavations of mines, is, I con- 

 ceive, the most influential, subject as it is in a peculiar degree 

 to be modified by local circumstances both in its quantity and 

 direction. It cannot however be doubted that it must chiefly 

 come from more elevated ground ; and therefore I think it 

 may be inferred, that the temperature of mines is not equal 

 to that of the earth at the same level, either in degree or in 

 uniformity. 



The temperature of water in the shafts of abandoned 

 mines has been repeatedly referred to in opposition to the 

 opinion that a native heat exists in the earth itself. On this 

 subject I have made some observations in a paper published, 

 in 1827, in the third volume of the Cornwall Geological 

 Society's Transactions, which I may perhaps be allowed to 

 quote. 



" My impression is, that the experiments which have been 

 made in these collections of water tend to support the opi- 

 nions" (in favour of a subterranean heat), " the differences of 

 temperature being considerable in different stopped mines ; 

 and even in different shafts of the same mine a variation of 

 temperature has been observed. 



" Some very shallow mines, it seems, have been found full 

 of water to the adit level at the temperature of 51; others, at 

 from 52 to 56, and even 57, as was the case at Gunnis 

 Lake copper mine, the depth of which was 125 fathoms, and 

 the adit 35 fathoms, from the surface; so that, taking the 

 mean temperature of the climate at as high as 51, (which, 

 from some experiments to be mentioned*, I now think is 

 rather above the mark, as it respects our principal mining di- 



** A series of observations, continued throughout the year, made on the 

 temperature of the ground, and three feet under the surface, gave for Dol- 

 coath 49-94 ; and Huel Gorland, which is more elevated, being about 

 350 feet above the sea-level, 48'99. 



stricts 



