FLO WAGE IN SUBCAPILLARY OPENINGS. 145 



is held by the pressure in the form of a liquid. But at temperatures 

 higher than 365° C, or the critical temperature of water, whatever the 

 pressure, the water is in the form of water gas. In this case it may be 

 suj:>posed to have a much greater penetrating power than in the form of 

 liquid, since it can not be considered as adhering to the walls of the 

 openings. 



Even if subcapillary openings be very small and the flow very slow, 

 it does not follow that the water within these minute openings is not an 

 agent through which important geological work is accomplished. The 

 water in such spaces is capable of taking into solution the substances with 

 which it is in contact, of depositing material from solution, of reacting' upon 

 the substances by hydration; in short, is capable of performing all the 

 transformations which freely moving water is able to accomplish. Indeed, 

 it has already been seen that all transfers of material between water and 

 rock must take place through the fixed films of water. (See p. 64.) 

 The transfer of material in subcapillary openings is confined to short 

 distances because there is no free circulating water. The interchanges of 

 material are probably slow, except between adjacent or nearly adjacent 

 mineral particles; therefore it seems highly probable that a given volume 

 of water in the subcapillary openings is far more effective in transforming 

 rocks than an equivalent volume in larger openings. The same reasoning 

 applies here as in the case of the capillary openings as compared with 

 supercapillary openings. The surface of action per unit volume in the 

 subcapillary tubes is vastly greater than in larger openings. As shown 

 on pages 686-698, the above conclusion as to the efficacy of water in 

 subcapillarv openings is fully justified by the facts. It is there seen 

 that the minute amount of water contained in the subcapillary openings is 

 the medium through which the complete transformation of rocks to schists 

 and gneisses has been accomplished. I therefore conclude that, while it 

 is probable that the actual flow of water and transfer of material in 

 subcapillary openings is comparatively slow, it is certain that most 

 profound alterations of rocks take place through this water as the agent of 

 transformation. 



Subcapillary openings include the openings of mechanical sediments 

 the particles of which, if spherical and of uniform size, are not greater than 

 0012 mm. in diameter. As a matter of fact, many of the openings in 

 mon xlvii — 04 10 



