270 CHAMBERLIN— THE AGE OF THE EARTH. 



to go. Doubtless other cycles follow in the sea and in the sedimentary 

 beds, particularly when deformations take place or igneous and meta- 

 morphic actions follow, but we need not dwell on these. 



The Cycles of Chlorine. — The climax of the solvent actions that 

 enrich the sea is reached in the cycles of chlorine, but only a passing 

 word can be given to these. The tenor of experiments with soils 

 indicates that chlorine remains more persistently in solution than the 

 sodium and associated substances. As the cycles of each substance 

 spring from its own nature and the conditions it encounters, the very 

 high preponderance of chlorine over sodium in the ocean finds its 

 chief explanation in this more persistent solubility. Its proportion 

 in average rock is only a conditioning factor and is not the chief con- 

 trolling influence. When compared with sodium, which is much more 

 abundant in the igneous rocks and indeed in the whole substance of 

 the outer ten or twenty miles of the earth shell, atmosphere, and 

 hydrosphere included,-^ the logical conclusion is that the cycles of 

 chlorine have always had a much larger liquid phase than those of 

 sodium, and that this has been cumulative through the ages. Chlorine 

 is better fitted than sodium to be used as a criterion of age, but even 

 in this last case there are formidable difficulties. Both sodium and 

 chlorine and all the other constituents, as already noted, have their 

 own histories which are difiicult to disentangle. As Roger Bell neatly 

 puts it : " There are as many histories to be written about the waters 

 as there are kinds of sediment." ^® There would be an ocean highly 

 charged with chlorides if there were no sodium in the earth at all. 

 So there would be an ocean highly charged with sodium solutions if 

 there were no chlorine in the earth. The status of the ocean at any 

 time is simply the equation of the solution phases of the antecedent 

 cycles of its constituents, all of which have passed through long, 

 complex, more or less individual histories. In the tedious work of 

 their disentanglement the older and simpler geo-chemical notions will 

 not answer; the newer principles of chemistry, physics, and geology 

 are indispensable. 



Conclusions. — Our finding, then, in respect to the age of the 

 earth from the geological viewpoint is this : 



2^ Clarke and Washington, ibid., p. 114. 

 28 Personal communication. 



