( 398 ) 
In the water of the lakes named under N°. 33 to 38, which are 
entirely surrounded by granite, basalt or gneiss, there are on the 
contrary no small quantities of sodium, with only traces of or very 
little chlorine. | 
So it appears that the process of chemical denudation, by which 
sodium is dissolved from silicates and conveyed by the rivers to 
the sea, is not going on, for the greater part, through the agency of 
chlorine. 
Now, in the sea water all the sodium being combined with 
chlorine and there having been since innumerable centuries a supply 
of sodium from the rivers with a deficit of chlorine, this deficit must 
have been provided for. It is known that continually there is 
hydrochloric acid gas poured in the atmosphere through volcanism. 
Considering that at least three-fourths of the rain falls into the 
ocean and only one fourth on the land it is easy to understand ir: 
what manner this deficit of chlorine is made up. 
Were it possible to find the annual absolute value of this deficit, 
did we know the average of it in river water, then we could, when 
starting from the uniformitarian point of view, and accepting that 
the ocean has acquired all its choride of sodium only in the actual 
way, estimate the geological age of the Warth, or better the length 
of past time of the process of denudation. 
The ocean contains, according to Dirrmar’s analyses and the 
newest estimates concerning the volume of the water in the ocean, 
21400 X 102 tons of chlorine combined with sodium. According 
to Murray’s estimate !) the rivers annually discharge somewhat 
more then 27 X 102 tons of water. Supposing a deficit of 1/000 ooo 
or 1 mgrm of chlorine per liter and admitting that on the 
land there took place 1/, of the total production of sodium chloride, 
those processes of chemical denudation ought to have proceeded with 
the same intensity during 590 million years (without this contri- 
bution of the land during 787 million years). The deficit however 
is on an average decidedly larger than a millionth part of the water. 
Were it nearly 25 mgrm per liter and did we again admit that on the 
land there is produced one-third as much chloride of sodium as in 
the ocean, then the results of our computation would agree with 
that of Lord KerLviN who estimated the age of the Earth to be about 
24 million years. The latter supposed deficit of chlorine seems 
however to be far above the real average. 
1) Le, p.70. As stated by Murray 6524 cubic miles, These are equal to 27192 KM? 
