SILVER AND GOLD, CONTINUED. 235 



manifesting itself. Flooded drifts, it was thought, had been 

 observed to grow hotter, and from this the hypothesis of kaolin- 

 ization was conceived. It was that the kaolinization of the feld- 

 spar in the deeply buried rock occasioned the heat of the lode. 



2.11.21. G. F. Becker (1879-82) comments on the excessive 

 alteration which the rocks have undergone, as it figures largely in 

 his hypothesis of origin. He then traces the results of faulting, 

 and shows that under conditions like those present the surface 

 would tend to assume a logarithmic curve, which coincides sur- 

 prisingly well with the present outline of the country. After 

 describing the lode itself, the origin of its metalliferous contents 

 is traced as follows. Waters under hydrostatic pressure from the 

 heights to the west are supposed to have percolated toward the 

 lode, passing through deeply buried regions of heat. They were 

 probably diverted from rising directly through the lode by an 

 impervious clay seam, and were thus forced to soak through the 

 diabase hanging, relieving it in passage of the metals, which were 

 afterward deposited in the higher portions of the lode. The 

 metals themselves were probably largely derived from the augite 

 of the rock. Mr. Becker had as an associate Dr. Carl Barus, who 

 studied the heat phenomena (especially the hypothesis of kaolini- 

 zation) and the electrical manifestations of the lode. The result 

 of Dr. Barus's careful experiments threw great doubt on kaolini- 

 zation as a source of heat. The electrical experiments were not 

 satisfactory. They were carried on also at Eureka, Nev., but no 

 very definite results were reached. 



2.11.22. The correct determination of the eruptive rocks 

 neighboring to the Comstock has been of great importance, not 

 alone because of their scientific interest, but as bearing on the fact 

 as to whether the lode itself was a contact fissure between two 

 di ffe rent rocks, or whether it was simply a fissure vein. It is 

 worthy of note that in connection with it Yon Richthofen de- 

 veloped one of the first important attempts to classify the vol- 

 canic rocks, and that Hague and Iddings have finally urged that 

 the peculiar crystalline structures of all eruptive rocks depend 

 primarily on the heat and pressure (i.e., depth below the surface) 

 under which they have solidified, destroying thus the time ele- 

 ment in classification. This is, to be sure, an old idea, but it gains 

 its best confirmation from the Comstock. Von Richthofen, in his 

 report to the Sutro Tunnel Company, and in his later memoir on 

 " The Natural System of the Volcanic Rocks " ( Gal. Acad. Sci., 



