SALINITY, GASES 47 



area, the salts of the ocean are derived from 

 all the land-surfaces and coasts of the globe. 



In 1887 the writer gave a table of the 

 average composition of river-water based 

 upon the composition of nineteen European, 

 Asiatic, and American rivers, and estimated 

 the amount of saline matter carried annually 

 into the ocean by rivers as nearly 5,000,000,000 

 tons. In 1910 F. W. Clarke made a similar 

 calculation, based upon more recent and more 

 extensive data, his result working out at about 

 2,700,000,000 tons, little more than half the 

 earlier estimate. 



We can form but a faint idea of the sub- 

 stances which were carried down from the 

 atmosphere when the first precipitation of 

 rain took place on our planet, or of the 

 composition of the sea-salts in the primeval 

 ocean. But the geological processes above 

 indicated have apparently been in operation 

 for millions of years. As a consequence the 

 salinity of the ocean is probably continually 

 increasing, but at such a very slow rate that 

 the change cannot be detected by our present 

 methods of analysis. Though the contribu- 

 tions of saline matter from rivers are large in 

 themselves, they are relatively small compared 

 with the vast accumulation of salts in solution 

 in the ocean into which they are diffused. 



The dissolved salts in river- water are 



