836 J. BARRELL MEASUREMENTS OF GEOLOGIC TIME 



mental difficulties* of the method lie, first, in the lack of knowledge as to 

 how much of the present sodium carried to the sea is newly derived from 

 igneous rocks; and, second, as to how the rate of supply compares now 

 with the mean for all geologic time. 



The suhject should not be dismissed so briefly, however, since the chief 

 publications in American geological literature in the past 10 years on 

 this subject have been those of Becker, and unless the validity of his 

 assumptious is carefully examined, his arguments will appear to possess 

 considerabk^ force. Becker has used Clarke^s data as the basis of new 

 calculations,*^" but introduces two new assumptions into the problem. 

 The amouut of sodium in metriic tons borne annually to the sea as de- 

 termined by Clarke foi'ms tlie basis of Becker's calcuhitions and may be 

 classified as follows : 



10.5 X 10** = cyclic sodium, wind borne from the sea. 

 99.0 X 10** = chloridized sodium of sedimentary rocks. 



3 . X 10" = sodium chloridized by chlorine of igneous rocks. 

 62 . 5 X lO*' = unchloridized sodium. 



175.0 X 10^^ total sodium annually borne to sea. 



Becker's first assumption is that the ratio of total oceanic sodium to 

 total oceanic chlorine, part of which is combined on precipitation witli 

 magnesium, potassium, and calcium, though partly ionized in solution, has 

 remained the same throughout geological time. This is contrary to the 

 expressed opinion of others, particularly A. C. Lane, who holds that the 

 ratio of sodium to chlorine was notably less in early geological times, with 

 the consequence that the early ocean waters were relatively rich in cal- 

 cium chloride. A lesser ratio of sodium chloride to other chlorides is 

 characteristic of the body fluids of marine as well as terrestrial animals 

 and suggests an inheritance of their physiological processes from an early 

 time, when in primitive animals the body fluids more nearly resembled 

 the surrounding medium. 



Becker's assumption requires that the annual amount of juvenile chlo- 

 rine added to the atmosphere from volcanic sources must be equal in 

 number of atoms to the annual supply of new . sodium derived from the 

 igneous rocks and dissolved from them mostly as bicarbonate — a postulate 

 which appears to be against the evidence. This permits him to take 

 32.5 X 10^ metric tons away from the 99.0 X 10*^ tons of chloridized 

 sodium and regard it not as former sea salt, but as new sodium derived 

 from igneous rocks and chloridized in the soil by atmospheric chlorine 



s" G. F. Becker : The age of the earth. Smith. Misc. CoU., vol. 56, no. 6, 1910. 



