236 GEOLOGY OF THE COMSTOCK LODE. 



aware of any analogy which indicates a likelihood that it is sufficient to 

 account for the heat phenomena of the Comstock Lode. 



Experiments on kaoiinization. — lu tho hopc of Tcaching uiore Satisfactory results 

 regardingkaolinization than observation or theoretical considerations yielded, 

 I requested Dr. Barns to ixndertake experiments with a view to testing the 

 asserted rise of temperature when the Washoe rocks are brought in contact 

 with water. 



Material selected. — The rock sclccted was from a mass cut by the Sutro Tun- 

 nel in the Savage claim, just before the tunnel strikes the vein. It is a dia- 

 base, and the freshest encountered under ground opposite that portion of 

 the Lode which has been considerably productive. It is described under 

 slide 1 8, and its analysis is given at the end of Chapter III. Lest it should be 

 objected that this rock had escaped decomposition through an exceptional 

 structure or a local variation in chemical composition, it may be remarked 

 that no trace of such a difference is perceptible either macroscopically or 

 microscopically, while its exemption from decomposition is fully accounted 

 for by the character of its occurrence. This mass, like most of the fresher 

 rocks in the District, is protected by clay seams which have prevented the 

 access of aqueous currents. The hanging wall of the Comstock is to so large 

 an extent obliterated by decomposition that many observant miners deny its 

 existence, but at this particular spot no vein-wall could be better defined. 

 It is marked by a compact smooth clay a foot or more in thickness, imme- 

 diately over which lies the mass of rock referred to. This is further pro- 

 tected, though not so clearly, by other clay-seams to the east, and is much 

 less shattered than the rock elsewhere. 



Method adopted. — The Tock was reduced to a gravel and placed within a 

 well-packed steam jacket. Steam was supplied from a boiler beneath, in 

 which the water was kept at a constant level and constantly boiling. The 

 difference of temperature between the rock and the inclosing steam was 

 measured by a thermopile. The electro-motive force was so compensated 

 that a variation of 0.001° C. was clearly indicated, and the experiments 

 extended over five weeks with only four interruptions. The whole plan of 

 the investigation was worked out by Dr. Barus, who will describe it in 

 detail in a separate chapter. The appliances at his command were few and 



