REDISTRIBUTION OF HYDROGEN. 983 



analyses of the freshest modern rocks usually show less than 1 per cent of 

 combined water. It follows that, in regarding 1 the original rocks as contain- 

 ing 1.92 per cent of water, the calculated amount of water for the hydration 

 of the sediments is too small. 



In the zone of anamorphism the dehydration of the rocks which have 

 been hydrated in the zone of katamorphism and passed into the zone of 

 anamorphism, is not complete. Even the coarsest schists and gneisses 

 ordinarily contain from 1.5 to 2 per cent of water. In so far as the process 

 of dehydration of the rocks, which have passed into the zone of anamor- 

 phism is incomplete, water has been abstracted from the hydrosphere. 



But even if the total of all the above could be estimated this would 

 give no idea of the amount of water which has been added temporarily to 

 the rocks by hydration during geological time. From the earliest time to 

 the present hydrated sedimentary rocks formed in the zone of katamor- 

 phism have passed continuously into the zone of anamorphism, and have 

 been steadily dehydrated. No data are available to estimate the amount 

 of water which has been added by hydration and liberated by dehydration. 



The question naturally arises as to what extent at the present time the 

 process of dehydration is reversing that of hydration. It seems certain 

 that hydration is taking place more rapidly than dehydration. While an 

 estimate of the amount by which hydration exceeds dehydration would be 

 very desirable, I see no way in which a quantitative result on this point 

 can be even approximated. 



While the amount of water abstracted from the hydrosphere by 

 hydration is large, it does not follow that the ocean is decreasing in magni- 

 tude; for the water continuously added to the hydrosphere by the liberation 

 of occluded water through volcanism and the crystallization of magma may 

 more than compensate for the losses due to hydration. 



ALUMINUM. 



Aluminum is the most abundant of the metals of the lithosphere. 

 Clarke's original estimate in 1891 was that aluminum constituted 7.26 per 

 cent of the lithosphere, hydrosphere, and atmosphere, all of this being* in 

 the rocks, of which it composed 7.81 per cent. Clarke's estimate of 1900 

 increases the amount in the original rocks to 8.16 per cent." It therefore 



a Clarke, cit., Bull. 78, p. 39; Bull. 168, p. 15. 



