260 CHAMBERLIN— THE AGE OF THE EARTH. 



degree. Thus the sodium now in the ocean is held to represent the 

 accumulation of all the geologic ages, and this total accumulation 

 divided by the rate at which the present streams are carrying sodium 

 down to the sea is held to give the age of the ocean, barring some 

 corrections to be noted later. The crux of the whole issue of age 

 lies in the validity of these concepts, particularly the irreversibility of 

 the sodium. 



The other view is far less simple. It looks upon the hydrosphere, 

 of which the ocean is the chief concentration, as only the liquid phase 

 of a solid-liquid-gaseous cycle through which the earth substances are 

 passing. It is held that the earth is perpetually undergoing self- 

 metamorphism in all its parts. This metamorphism takes place in a 

 multitude of ways, each unit doing its part, in its own place, in its 

 own way, and at its own rate. Each unit passes through its own 

 cycles of liquid-solid-gaseous states according as its nature, its con- 

 tacts, and conditions determine. Its career is wholly dependent on its 

 own succession of conditions, and is only affected by what other units 

 are doing under their conditions incidentally as it happens to come 

 into working relations to them. The cycles that thus arise are so 

 multitudinous and intricate that their correlation is a most formidable 

 task which is scarcely yet fully appreciated ; little more than a begin- 

 ning has been made toward its accomplishment. 



Under this view it is necessary to stress the fact that the simple 

 solid-to-solution change from the rock to the ocean does not cover 

 the whole evolution in the case of any substance. In most cases there 

 are many cycles, some in parallel lines, some in succession. The 

 content of the indurated rocks, on the one hand, and the content of 

 the sediments and the ocean solutions on the other, are great features 

 that have guiding value, but they are too general to cover with ade- 

 quate accuracy the sub-cycles that make up the real history. The 

 correlation of the whole is too largely conditioned by the number and 

 speed of the constituent cycles to be successfully dealt with. It is 

 especially affected by the reversals from the liquid to the solid state 

 which take place during the passages from rock to soil, from soil to 

 fresh-water solutions, or to colloids and turbid suspensions, and from 

 these to the concentrated sea solutions in the borders of the sea. The 



