AGE OF EARTH AND SALTNESS OF SEA 193 



sodium in the sedimentaries had its origin in the sea. Then the 

 problem of salt beds must also be considered. That a considerable 

 proportion of the salt deposited in lakes is cyclic, and had its origin 

 in the sea may be regarded as established. But what would happen 

 if such a salt bed were subject to metamorphic action ? It is obvious 

 that not only would the sodium enter into the composition of the 

 metamorphic rock, but that it would do so out of all proportion to 

 the chlorine. Such a volatile constituent as chlorine is bound to be 

 evolved in the form of some compound of lower boiling point than 

 salt. Indeed, is it not possible that a proportion of the large quanti- 

 ties of hydrochloric acid, ammonium chloride, and aluminum chloride 

 evolved during volcanic action may have their origin in this manner ? 

 If this speculation were true, it is quite possible that the cyclic sodium, 

 using the term in its widest significance, might exceed the cyclic 

 chlorine, and that the calculations would be still further vitiated. 



Without laying too great stress on this speculation, it must not 

 be forgotten that uncertainties of this kind exist, and that the sea- 

 salt method must not be regarded as of greater validity than those 

 founded on pure geology. The method is liable to a number of 

 uncertainties and it would not be wise to lay too great stress on this 

 particular estimate. It is highly probable, however, that this method, 

 when based on more accurate analyses, may act as a check on the 

 results obtained from, pure geology, from radioactivity, and from 

 other lines of attack. Nor must it be forgotten that this method,'' 

 even if in the future it should be superseded, was the first serious 

 attempt to get outside the vicious circle of the classical physical 

 three methods, which have proved such a barrier to the progress of 

 geologic thought on this fascinating cosmic problem. 



I In making this statement, the interesting investigations of Mr. Mellard Reade 

 on the evolution of carbonate of Hme must not be forgotten. This may ultimately 

 prove of greater value than the sea-salt method. Unfortunately, in his later years, 

 this author published other methods, based on less reliable data, which gave a smaller 

 minimum for geologic time. His most valuable work was thus forgotten. 



