of the United Mines, 101 



vious to it. Ill these instances, at least, there are no grounds 

 for supposing that any chemical decomposition of the sulphur 

 ores in the lode has caused the high temperature of the wa- 

 ter, or contributed to it in any degree, seeing that it contains 

 no metallic, and scarcely any sulphate salt. 



The difference in the heat of the two springs may perhaps, 

 in part, be attributed to the tendency of the warmer currents 

 to rise towards the upper wall of the lode ; and still more to 

 that of water at a much lower temperature passing from su- 

 perior strata down upon the inclined surface of the lower 

 wall, where, mixing with the water rising from below, the 

 temperature becomes modified, as well as the proportion of 

 the saline contents. 



It cannot be doubted that ascending and descending cur- 

 rents of water, more or less copious, and at different degrees 

 of temperature, abound in the veins and fissures of the earth, 

 and often at the junctions of different rocks, and that they 

 must have a great influence in modifying the subterranean 

 temperature, and in different degrees in different places. 



Common salt is of rare occurrence in our mines ; its pre- 

 sence in the water in question cannot well be attributed to 

 the flowing of sea-water into the excavation, in consequence 

 of its local or direct pressure ; for if some miles of distance 

 from the coasts did not render this highly improbable, the 

 considerable streams at very high temperatures, and very con- 

 stant too (as appears from observations made at different 

 times), are facts not consistent with such an explanation. If 

 the subterranean jets of water were caused by the inroads of 

 a neighbouring sea, we should expect to find them at compa- 

 ratively low temperatures, aud these diminishing in propor- 

 tion to the duration and amount of the influx. 



The salt may, however, have been derived from the ocean, 

 in consequence of the latter penetrating into the earth at its 

 greater depths, or even at its lesser ones, which, under dif- 

 ferent given circumstances, it may be supposed to do. In 

 either case, the salt water would, from its superior specific 

 gravity, have a tendency to descend through the heated and 

 less saline water in the veins, fissures, &c., where i\\Q fluids 

 becoming gradually more or less mixed and extended in dif- 



