CHAPTER VII. 



HEAT PHENOMENA OF THE LODE 



Skction 1. 



GENERAL DISCUSSION. 



High temperatures of the mines. OllC of tlie peCuHaritieS foi' whicll the CoM- 



STOCK Lode has been famous ever since deep mining began upon it, is the 

 high temperature of the rock and of the water encountered. In this respect 

 it stands alone among ore deposits, though water heated to 125° F. has 

 been encountered in the Clifford mine in Wales, and very hot water is found 

 in the superficial workings of the cinnabar deposits in the coast range of 

 California. On the 3,000-foot level of the Comstock floods of water have 

 entered the mines at 170° F. Water at this temperature will cook food, and 

 will destroy the human epidermis. Even a partial immersion in it is there- 

 fore fatal. In spite of very rapid ventilation, the air in the underground 

 galleries is often intensely heated and is nearly saturated with aqueous 

 vapor. Many deaths among tlie miners have occurred from prolonged 

 exposure to these unnatural conditions, which also add immensely to the 

 difficulties of geological exploration. 



Normal increment of heat. — A great many iuvestigatious have been made during 

 the last years, in many parts of the world, on the increase of the temperature 

 from the surface of the earth downward. The observations have not resulted 

 in establishing a uniform rate of increase in any locality, nor is such a result 

 to be expected from any future observations. If the temperature is deter- 

 mined in a freshly drilled hole the record will necessarily be too high, 

 because tlie surrounding rock is heated by the mechanical action of the drill. 

 But the moment the rock is jilaced in communication with air from the 

 surface, or with water from higher levels, it begins to cool off. Rocks are 



