292 



GEOLOGY OF THE COMSTOCK LODE. 



composition resulting in a normal case. Believing, therefore, that the phe- 

 nomena of kaolinization are reproduced at all temperatures below a certain 

 limit, and that the difference in effect is merely quantitative, the rock in 

 the experiments here described was subjected to steam at the boiling point 

 of water on the Comstock.^ Besides this, it was intended to modify the 

 method of reseai'ch sufficiently to trace the action of superheated steam 

 also. This must, however, be reserved for a future report. 



Fig. 19.— Boiler (scale oue-fifth). 



Apparatus. — The apparatus (a boiler) in which the rock was subjected to the 

 action of steam is shown in longitudinal section, on a scale of one-fifth, 



' Abont 93° C. 



