WATER OF ZONE OF ANAMORPHISM. 661 



in the openings, tins would reduce its chemical activity; but the fact that 

 the viscosity of the gas is probably less and its temperature higher may 

 render a small quantity of water in the form of gas as potent or even more 

 potent in the transformation of rocks than a much larger amount as liquid. 



QUANTITY OF WATER. 



The quantity of water in the crystallized rocks of the zone of anamor- 

 phism is certainly small as compared with that in the belt of cementation. 

 It has been explained that the openings of the zone are normally of sub- 

 capillary size, although some of them are as large as capillary openings. 

 The quantity of water is therefore limited to the space which may be 

 furnished by these openings, unless it be supposed that under the extra- 

 ordinary pressures and high temperatures which prevail in this zone the 

 water gas finds a place between the molecules of the crystallized minerals, 

 and this hypothesis can not be proved. Ignoring this possibility, it is 

 probable that the amount of free water in the forms of liquid and gas in 

 the zone of anamorphism is in most cases less than 1 per cent. 



CIRCULATION OF WATER. 



Before the question as to the circulation of the water in the zone of 

 anamorphism can be satisfactorily discussed, it is necessary to answer the 

 question as to the probable sources of the water. The certain sources of 

 water in the zone of anamorphism are (a) the water mechanically contained 

 in the rocks at the time they passed into the zone, (b) water produced by 

 dehydration of hydrous minerals, and (c) water from igneous intrusions. 



(a) The sediments as originally formed commonly contain larg*e 

 quantities of water in their interstices. As explained on pages 124-127, this 

 amount by volume is frequently 25 per cent or more. By deep burial the 

 sediments pass into the zone of anamorphism. In most cases it is highly 

 probable that before this takes place the larger portion of the original 

 water has been lost as a consequence of consolidation and cementation. 

 But it is not likely that all of the water is lost, and therefore the sedimen- 

 tary rocks as they pass into the zone of anamorphism probably carry with 

 them mechanically mingled water. As to the quantity of this water, no 

 certain knowledge is available; but I suspect that in the majority of cases 

 it is small, possibly less than 1 per cent. Doubtless the rocks of the centro- 



