734 C. R. VAN HISE 



by crushing. It is highly probable that few openings of appre- 

 ciable magnitude exist at depths so great as 10,000 meters. 



Therefore from the principles of physics and from observa- 

 tion we conclude that crevices and cracks of considerable mas - - 

 nitude do not exist below a very moderate depth. I would not 

 say that minute cavities filled with liquid do not exist in the 

 zone of rock flowage ; I would not say that very small openings 

 filled with gases may not exist in that zone ; but there is every 

 reason to believe that such cavities are exceedingly small. 

 And it is well known that ore deposits in order to be of 

 economic value must be of considerable magnitude. Such 

 deposits were not formed in the minute and discontinuous open- 

 ings filled with gas or liquid which very possibly exist at great 

 depth. 



But let us now consider this subject from another point of view. 

 You as engineers know very well that the friction of a moving 

 liquid increases very rapidly as the size of the passage through 

 which it moves decreases. This is true even of super-capillary 

 tubes. It is still more true of capillary openings, and the 

 resistance goes up very rapidly as the capillary tubes decrease 

 in size. When the openings become so small that the molecu- 

 lar attractions extend from wall to wall or the openings are sub- 

 capillary, the resistance is so great that the flowage is practically 

 nil. 1 Now it is perfectly evident that a deposit of mineral 

 material in an opening is not the work simply of the water that 

 occupied it at any one time. Ordinarily, underground solu- 

 tions of silica do not contain upon the average more than one 

 part of silica per 100,000 parts of water, so that if an open- 

 ing be filled with quartz, the most abundant of all the gangue 

 minerals, we must suppose at least 100,000 times as much 

 water went through the opening as there was quartz deposited. 

 Therefore it is perfectly clear that the material for large ore 

 deposits can only be gathered and the ores deposited in the zone 

 where there is a vigorous circulation, and vigorous circulation is 



1 Metamorphism of Rocks and Rock Flowage, by C. R. Van Hise : Bull. Gcol. 

 Soc. Am., Vol. IX, p. 272. 



