668 A TREATISE ON METAMORPHISM. 



The next question of importance is the probable movement of water 

 between the zone of anamorphism and the centrosphere. We know nothing 

 as to the average comparative amount of water in the openings of the lower 

 part of the zone of anamorphism and in the openings of the centrosphere 

 below, nor do we know the pressures and temperatures to which the water 

 is subjected. If the amount of water in the centrosphere be as great as it 

 may be supposed to be from the quantity in the extrusive lavas, it is press- 

 ing' upward toward the surface, driven by the enormous pressure and high 

 temperature to which it is subjected. Are the quantities of water in the 

 crystallized zone of anamorphism, combined with the pressures and tem- 

 peratures there, sufficient to give to the water an equally strong tendency 

 to move downward? Whether water makes its way into the zone of ana- 

 morphism from the centrosphere below, or moves in the reverse direction, 

 would depend upon the relative force of these two tendencies. Since we 

 know nothing of the quantity of water in the centrosphere, but little as to 

 the condition of the material of that zone, little of the temperatures there 

 prevailing, and absolutely nothing as to a change in the condition of the 

 material in passing from the lithosphere to the centrosphere, I do not 

 venture to express an opinion as to whether or not water travels upward 

 from the centrosphere into the zone of anamorphism. So far as the analogy 

 between the zone of anamorphism and the belt of cementation has any 

 weight, it indicates an upward rather than a downward movement. The 

 permanence of the ocean might be adduced as evidence of the gradual 

 although slow movement of water from the centrosphere to the zone of 

 anamorphism, and from the zone of anamorphism to the belt of cementation, 

 and thence to the surface, rather than a reverse movement. But this move- 

 ment may be accomplished mainly by volcanism rather than by circulation 

 through the solid rocks. 



VARIABLE MATERIALS AND CONDITIONS. 



The rocks of the zone of anamorphism include various classes: (1) All 

 kinds of plutonic igneous rocks may be found in the zone v of anamorphism. 

 Indeed, the lower zone is especially the zone of the plutonic igneous rocks. 

 It is in this zone that the great batholiths form. Chemically they vary 

 from the most basic to the most acid, and mineralogically they are 

 correspondingly variable. (2) All kinds of sedimentary and all kinds of 

 volcanic rocks may pass into the zone of anamorphism by deep burying. 



