SEA-SALT AND GEOLOGIC TIME 59 



when there is any reason to ascribe special accuracy to river- 

 water analysis, the excess of sodium diminishes and tends to 

 vanish. Prof. Dubois 1 collected a number of good analyses, 

 tabulated them, and inferred from them, according to Prof. Joly's 

 method, a geologic time of 400 millions of years. The inference 

 he made, as he was a believer in Lord Kelvin's methods, was 

 that the original sea was salt. The true inference is that the 

 method is of no value. Within the limits of experimental error 

 you can deduce any value you please. 



Though the previous discussion renders it unnecessary, it 

 is as well to mention one other point. The assumption that no 

 sodium returns from the sea to the rocks is unwarranted. 

 Indeed one instance to the contrary can be mentioned. It is a 

 recognised fact that much of the salt in the salt lakes, and 

 inferentially in salt beds, is windborne and has its origin in the 

 sea. But what would occur when strata containing salt beds 

 are subject to metamorphosis or are absorbed by the magna? 

 Is it not obvious that the sodium would be added to the content 

 of the rocks and that the chlorine would be expelled as some 

 volatile compound ? Indeed, is it not probable that some 

 portion of volcanic chlorine has this origin ? Again, with regard 

 to the ordinary processes of the formation of sedimentary rock, 

 we do not know enough to say that no dissolved sodium is 

 reabsorbed. 



This speculation, however, is a side-issue, and is not neces- 

 sary to the argument. Were the analyses of sufficient accuracy, 

 were the method in general valid, such matters would require 

 careful consideration. At present, without taking such remote 

 speculations into account, we can still say that the sea-salt method 

 is absolutely worthless. It is based on a misapprehension ol 

 the data on which it rests. It is an instance of the care that is 

 required when results are transferred from one branch of science 

 to another. With regard to geologic time, the value of radio- 

 active methods is still to be determined. The value of the sea- 

 salt method, like the still more famous ones of Kelvin and Tait, 

 is nil. 



1 Proceedings Amsterdam Academy, 1904. 



