HEAT PHENOMENA. 241 



heated rock in contact with sedimentary material. The well-known reac- 

 tions which take place under such circumstances in the presence of water 

 have produced solfataric gases as long as the supply of sulphates and of 

 reducing agents held out. Of these there is now a mere trace. Whether 

 this highly heated rock is part and parcel of the surface rocks of the 

 Washoe District is a question which can only be answered in terms of 

 probabilities; yet as these rocks must have come from a focus of volcanic 

 action in about the same vertical line, the chances are certainly in favor of 

 the supposition that the high temperature of the Lode is a later member of 

 the series of phenomena, of which the ejection of the younger hornblende- 

 andesite, or possibly of the basalt, was an early manifestation. 



The rocks all moist. — Thc disscmiuation of heat through the rocks of the 

 CoMSTOCK has been regarded by one geologist as a point very difficult of 

 explanation. He regarded the rocks as dr}", and assuming their conductivity 

 to be the same as that of the Calton Hill trap, which Sir William Thomson 

 has made famous, he found the transmission of heat insufficient to account 

 for the facts, The rocks are in great part dry, as miners use the word — i. e., 

 many exposures do not drip water; but though paying especial attention to 

 the subject, I found none which were not moist. Chips and specimens, for 

 example, always changed color after half an hour's exposure to dry air, 

 except when taken from flakes which were already partially separated from 

 the mass and exposed to a di-ying current. The rocks of the District are 

 not glassy but crystalline, and that such rocks in the immediate neighbor- 

 hood of vast bodies of water at pressures equivalent to a head of, say, from 

 1,000 to 3,000 feet, ever since they cooled many thousand years ago, 

 should remain dry, would be strange indeed, and quite opposed to all that 

 is known of the permeability of rocks by water. But when it is taken into 

 consideration that far more than 99 per cent, of this rock is highly decom- 

 posed, it is almost inconceivable. 



Source of the water unexplained. — The sourco of the watcr coiiveying the heat to 

 the CoMSTOCK is somewhat mysterious. The country is a sage-brush desert, 

 and the rainfall is not over ten inches. The slopes are steep and the evapora- 

 tion immense. The mines are now so deep that they might drain a large 

 extent of country, but great quantities of water were met with when the 

 workings were within a few hundred feet of the surface and could appar- 



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