AGE OF EAETH AND OCEAN — KNOPF 201 



this factor, Lane shows that the age of the ocean might be as much 

 as three times the length usually estimated by the sodium method. 



The coefficient of solvent denudation obtained by Clarke, 68.4 

 metric tons, does not differ nuich from that which Reade got in his 

 pioneer attempt, 100 tons. Of this 68.4 tons, 5.79 per cent is sodium. 

 Therefore, the quantity of sodium carried each year to the ocean is 

 1.58X10** tons. Dividing this amount into the total oceanic sodium, 

 we obtain as a first approximation to the age of the ocean according 

 to the sodium method, 100,000,000 years. 



The quantity of sodium annually delivered to the ocean, however, 

 is not all a new addition to the amount already there. Part of it 

 has been there before : this part is the so-called cyclic sodium. The 

 most obvious form in which cyclic sodium occurs is as salt spray 

 that has escaped into the atmosphere, has been carried inland, and has 

 returned by the way of precipitation and drainage. Opinions differ 

 sharply as to the corrections that should be applied for the wind- 

 borne sodium. Joly allowed 10 per cent. Becker, by assuming 

 that the wind-borne sodium chloride becomes nil at 20 miles inland, 

 allowed 6 per cent, and Clarke follow^s him. Holland, however, 

 has shown that in Rajputana, India, salt is carried inland 500 miles 

 by the wind. Moreover, long extended series of determinations of 

 the chlorine in the precipitation at Mount Vernon, Iowa, which is 

 1,500 miles from the Pacific coast, 1,200 miles from the Atlantic 

 coast, and 800 miles from the Gulf, prove that salt may be carried 

 great distances inland in quantity sufficient to account for all the 

 chlorine shown by river-water analyses. The average of several long 

 series of determinations by Wiesner, I^Jiox, Artis, and Peck is 7 

 parts per million. The nuiximum amount in any one rain storm was 

 21 parts i^er million. Hendrick's recent result (1927) is somewhat 

 lower, being 5 parts per million, but his maximum — 121 parts per 

 million — is much higher than any previous maximum. It would 

 be interesting in future determinations to correlate the chlorine 

 content with the origin of the storm that brought the precipitation, 

 whether from the Pacific or the Gulf coast. Inasmuch as two- 

 thirds of the precipitation evaporates and passes into the atmosphere 

 practically free of chlorine, the other third, the run-off, should con- 

 tain three times as much chlorine as the average amount in the pre- 

 cipitation. As a matter of fact, the drainage of the Central States 

 does not carry so much chlorine, and consequently there is an unex- 

 plained discrepancy. 



That portion of the sodium which is balanced by chlorine, the 

 chloridized sodium, as it is called, may therefore be excluded as 

 being cyclic sodium. As shown later, this exclusion is not wholly 

 justified, as part of the chlorine in the precipitation is of volcanic 



