524 THE DISTRIBUTION, ETC., OP ALKALINE ROCKS, 



Professor Joly makes two assumptions — (1) that erosion has 

 taken place at a uniform rate; (2) that the primitive ocean was 

 less alkaline than the present. Both these premisses are debatable, 

 but they need not be further argued here. 



Joly's discussion of the fact that F. W. Clarke (U.S.A. 

 Geological Survey) has shown that old metamorphic and igneous 

 rocks contain more alkali than modern eruptives, need not be 

 debated, as it is quite in accord with my theory. 



Professor Joly goes on to show that by raising the earth's 

 temperature to 1500° the metals Fe, Mg, Ca, K, and Na can 

 exist only as* silicates, and the atmosphere would consist ot H 2 0, 

 C0 2 , H, and HC1. NaCl would be unstable. Then he proceeds 

 to show that when the temperature fell to 370° the waters would 

 condense and there would be a sensible shrinkage due to cooling. 

 The water would gather into depressions, and the increased 

 pressure over the oceanic areas would squeeze out the magmas 

 over the land. The acid waters acting on a magma of dioritic 

 composition would take up elements in the following proportions: 

 Fe4-71, Ca 3-53, Mg. 2-64, K 235, Na268; hence only 14% of 

 the salt in seawater was NaCl. 



The arguments all seem to be very debatable. Acid waters at 

 a temperature of from 100° to 370° would exert great solvent 

 power on the rocks which they covered, and especially where they 

 fell as rain. The ocean being for a long time at the higher 

 temperature, it would take enough substance into solution to 

 become supersaturated as the temperature fell. Hence some of 

 the earliest sediments would be chemical precipitates. The 

 amount of C0 2 * in the atmosphere and in the sea being greatly 



* F. W. Clarke has estimated the chemical composition of the earth's 

 crust with the following result : — 



Cr. ..A 



Ni ... I 01 



CI ... [each. 



F . 



Most of the C would have existed in the primitive atmosphere as C0 2 . 







.. 47-02 



Si 



.. 28-06 



Al 



.. 8-16 



Fe 



4-64 



Ca 



.. 350 



Mg 



.. 202 



Na 



.. 2-63 



K 



.. 2-32 



Ti 



041 



H 



. 0-17 



C 



0-12 



P 



0-09 



Mn . 



. 0-07 



S 



. 0-07 



Ba 



0-05 



Sr 



, 0-02 



