230 GEOLOGY OF THE COMSTOCK LODE. 



the natural distribution of the waters, and consequently also of the heat, is 

 further indicated by the immense pressure which the water often shows on 

 being tapped by the drills in the lower levels. This not infrequently 

 amounts to a head of several hundred feet. 



Scattered observations cannot agree closely. — Taking these clrcumstances iuto Consid- 

 eration, it appears to me impossible to reach any accurate result by discuss- 

 ing in detail the fluctuation of the temperatures observed at different times 

 in different portions of the Lode. Before ground was broken considerable 

 variations probably existed in consequence of the presence of convection 

 currents. Under the present conditions it appears from the foregoing that 

 great fluctuations from a regular law of increase, and great anomalies which 

 cannot be immediately traced to their sources, must inevitably occur. 



A first approximation from such data. BarOU V. Richthofcn, althoUgh iuslstiug 



strongly on the abundant evidences of solfatarism, mentions no abnormal 

 temperatui'es. Mr. King gives a table of observations, from which it ap- 

 pears that the average temperature of the mine waters, from the surface to 

 the 700-foot level, is between 70° and 75° F. At a depth of about 1,100 

 feet he found water at 108° F. Mr. King remarks : "That to the waters is 

 due the temperature of the whole interior of the Lode is evident from the 

 fact that they average a few degrees higher than the clays or rocky mate- 

 rial." He notes only one instance in which the rock and water showed the 

 same temperature. Mr. Church made many careful observations, which he 

 has very fully discussed. He estimates the mean tem^^erature of freshly 

 exposed surfaces on the 2,000-foot level at 130°. The water with which 

 the Gold Hill mines were flooded in the winter of 1880-81 entered on the 

 3,000-foot level. It was repeatedly tested by the officers of the mines, and 

 by myself, and was found to have a temperature of 170° F. This water 

 was first struck at a depth of 3,080 feet, by a drill hole from the bottom of 

 the Yellow Jacket shaft. Taking into consideration that 170° is not an 

 average, but probably a maximum for this depth, these data indicate 

 roughly a nearly uniform increase of temperature of about 1° for every 28 

 feet.' If the attempt be made to discuss the observations in detail, great 

 irregularities will be found. As Mr. Church very pertinently remarks, " the 



' More exactly an increase of 1° in 28.7 feet for the interval of 1,650 feet between the 350-foot and 

 the 2,000-foot levels, and of 1° in 27^ feet for the 1,100 feet between the 2,000 and 3,100-foot levels. 



