CHAMBERLIN— THE AGE OF THE EARTH. 265 



are not predetermined solely by the composition of the igneous rocks 

 now at the surface, but rather by the relations of their own solvent 

 to their non-solvent natures under the conditions of their long com- 

 plex history. Specifically, in the case of sodium and chlorine, the 

 observed ratio merely means that the solution stages of sodium com- 

 pared with its solid stages are much inferior to those of chlorine, just 

 as those of potassium are much inferior to those of sodium, and so 

 on through the list. But, however cogent this may be, definite evi- 

 dence that sodium does enter freely into the cyclic processes, in due 

 proportion to the action of its associates, however inferior the pro- 

 portion may be, will naturally be demanded. Allusion has already 

 been made to a neglected factor. Let us turn to that. 



The Mud Cycle Actuated by the Surface Floods. — Familiar as 

 this is in many respects, it has perhaps received less critical geo- 

 chemical study than almost any other common feature of nature with 

 which we are directly, not to say unpleasantly, brought into contact. 

 The agricultural chemists have naturally been preoccupied with those 

 elements of the soils that serve as plant food, the students of hygiene 

 and domestic science, with waters suitable for drinking and culinary 

 purposes, and the geologic chemists with the organic extracts and 

 precipitates that form the limestone, dolomites, and siliceous beds. 

 The mud factor of the surface wash has been neglected. And yet 

 the muds (later shales) comprise much the largest part of the solid 

 residue of disintegration. This solid disaggregated residue and the 

 colloids associated with it are separated from the true solutions in 

 large measure at the very start on their long journey to the sea. 

 The true solutions are largely formed by waters that descend through 

 the soils into the underlying formations and thus form the ground 

 waters which pass by springs and seeps into the streams, giving them 

 their steady supply of clear water. This is the water chiefly analyzed 

 and taken into account in reckoning the material borne by the stream 

 to the ocean. The solid residue, the clays, silts, and sands, however, 

 are only slightly removed by the gentler rains which soak into the 

 ground. They are carried down to sea chiefly by the floods following 

 heavy storms, or by the thaw-waters of winter snows which form the 

 spring freshets, or by flood stages from any cause. The turbid mat- 



