SUMMAET. 397 



quartz body is an opening to receive it. The group of mines worked througli 

 the Union shaft and tlie Jacket, Crown Point, and Belcher mines show peculiari- 

 ties of structure which point to the likelihood of such o])enings at lower levels. 

 Openings such as that which contained the Consolidated Virginia and Cali- 

 fornia bonanza, however, give almost no warning of their approach from 

 above, and may at any time be struck in the intermediate mines; but a 

 series of bodies nearly on one level, such as were found in the secondary 

 fissure (the "Virginia vein") is not likely to recur. 



THE THERMAL EFFECT OF KAOLIXIZATION. 



Kaoiinization hypothesis. — Thc vlcw that the heat of the CoMSTOCK is due to 

 the kaolinization of feldspar is new and ingenious, but purely speculative, for 

 there is no unquestionable, direct evidence in support of it; while the process 

 is so complicated and so little understood that there is abundant room for 

 difference of opinion in any discussion of the theory involved. Dr. Barus 

 contrived and executed experiments to test the assertion that a rise of tem- 

 perature followed the action of heated waters from the east-countr}- rock 

 of the CoMSTOCK. These experiments he has described and discussed in 

 Chapter IX. 



The thermal efi'ect of kaolinization may be defined as the quantity of 

 heat generated by the action of the aqueous vapor on the unit mass of the 

 given feldspathic rock in the unit of time. It is to be regarded as a function 

 of the percentage quantity of feldspar originally contained in the given 

 rock, and of the temperature of this material, as well as of the time during 

 which the action has been going on. A priori the thermal effect may be 

 either positive, negative, or zero. The expei'iments were undertaken to 

 ascertain in how far the fundamental principle of the kaolinization hypothesis, 

 namely, that the thermal eft'ect is positive, agreed with facts. Such a research 

 was also desirable because of the intrinsic interest which attaches to the 

 question. 



Considered from a physical point of view, the question is rather a diffi- 

 cult one, and of a kind in which satisfactory results can be reached only 



