46 On the Temperature of Mines. 



streamlets from the roofs of deeper levels ; and in either case, 

 it must produce more or less influence on the temperature, 

 and prevent its being unifonn at equal depths. If tliere were 

 a perfectly free and open conmiunication between the various 

 jiortions of water under the surface of the earth, it is evident 

 that mines could not be drained, but the pressure of the co- 

 lumns of water would be irresistible, and their impetuosity over- 

 v.'helming." 



" The high temperature in mines seems to have no necessary 

 connexion with the minerals which they contain : even where 

 iron ])yrites is very abundant, the heat does not appear to be 

 greater than where it is the reverse." 



" Having recently tried some experiments on the water 

 taken i'rom the bottom of several deep mines, I find it in most 

 instances to contain in solution a very minute quantity of any 

 foreign substances, varying perhaps from one to five or six 

 grains in a pint. Its relative purity appears to have no re- 

 ference to the depth or temperature of the mines ; for instance, 

 Huel Abraham and Dolcoath are the two deepest and two 

 of the warmest mines in the county, and the water from the 

 bottom of these mines does not in either case hold in solution 

 more than about two grains of foreign matter in a pint. On 

 the other hand, some mines abountl with much less pure wa- 

 ter: that from the Consolidated Mines leaves ten grains of 

 residuum from a pint ; Huel Unity, sixteen grains ; Irom one 

 shaft in Poldice, nineteen, and from another ninety-two grains, 

 from the same quantity. In most of the mine-water that I 

 have examined, the muriatic salts, especially the mm'iates of 

 lime and of iron, are most abundant. I have detected muriate 

 of soda in some instances, particularly in the water Irom the 

 bottom of the United Mines, the Consolidated Mines, Huel 

 Unity, and Poldice." 



" Out of the 92 giiiins of residuum, produced from a pint of 

 water from one of the engine shafts of the latter mine, 24 

 grains proved to he muriate qf soda ; 52 grains the muriates 

 of lime and magnesia, chiefly the former; and the remainder 

 muriate of iron, and a small quantity of the sulphate of lime. 

 The water from another engine shaft of the same mine con- 

 tained 5i- grains of muriate of soda, and about 13 grains of 

 the muriates of lime and magnesia, and the carbonated oxide 

 of iron." 



" All the mines above enumerated are situated in the inr 

 terior of this part of Cornwall, and are distant several miles 

 from the sea ! " 



[To be continued.] 



XI. The 



