232 GEOLOGY OF THE COMSTOCK LODE. 



contact with these rocks is of constant occurrence in the mines, and is 

 offered, in fact, whenever a pump breaks or is stopped for any reason, and 

 water rises upon a partially decomposed seam. A case of this kind in the 

 Caledonia is of more than ordinary interest, for the reason that this was a 

 cool mine, both rock and water being but little above ordinary tempera- 

 tures. The heat of the air in the drift was probably not above 90° F., but 

 after lying twenty-four hours under water a very marked change took place. 

 The water had reached a thick seam of the kind that is solid enough when 

 dry, but swells with great force when wet. The 1 2-inch timbers were all 

 splintered, and the temperature of the level had risen probably to 110°, 

 though no observation was taken. Still the fact of increased temperature 

 and of increase from this cause alone was undoubted. Since that time the 

 Julia, Savage, and Hale d Norcross mines have all been flooded and subse- 

 quently di'ained. The Norcross has a fine current of fresh air, and I have 

 not observed any complaint of its condition, but both the other mines were 

 reported to be extremely hot after their submersion. They were very much 

 above their usual temperature, and work was frequently stopped to allow 

 them to cool down. Such evidences cannot take the place of exact labora- 

 tory experiments, but they are just as incontestable proof of the fact of 

 heat, and high heat, from kaolinization, as if we had its precise measure." 



Criticism on the evidence. — It wiU be observed that it is not stated when the 

 flooding of the drift in the Caledonia occurred, or who estimated the temper- 

 atures; nor yet whether the water of this particular flood was warm or cold. 

 With regard to the flooding of the Julia, Savage, and Hale d Norcross 

 mines, the only event of the kind known to me was that which occurred in 

 1 876. This flood lasted for three years. Soon after its commencement an 

 official report of the supex-intendent gave the temperature of the water at 

 139°, and Mr. Church reports it later (apparently early in 1878) as 154°.' 

 The great heat of these mines appears to require no further explanation. 

 I am not able to confirm the observation that flooded drifts grow hotter, 

 except when the water of the flood enters the workings at a high tempera- 



' This cbauge of temperature is not remarkable aud bas not been advauced in favor of the chem- 

 ical theory of the heat, for many millions of gallons were pumped from the flooded mines. Streams per- 

 colating from a large body of heated water through new channels in comparatively cool rock will at 

 first be cooled ; but they will grow warmer as the rock is gradually raised to the temperature of the 

 water at the source. 



