276* THE POPULAR SCIENCE MONTHLY. 



through some natural duct, finds its way to the sea with its bur- 

 den of salt. But when the waters of the ocean are evaporated to 

 form clouds and rain, the salt is left behind, so that ever more and 

 more salt is being transferred from the land ; and this ceaseless 

 transfer has been going on since the first brooks and rills gath- 

 ered together to form the rivers of the primeval lands. This pro- 

 cess of salinification, which is identical with that which takes 

 place in every lake and inland sea, like Great Salt Lake and 

 the Dead Sea, into which streams flow but from which none 

 emerge, has often been looked upon as a sufficient cause for the 

 existing saltness of oceanic waters, for the ocean occupies a great 

 closed basin into which many thousands of rivers flow, but from 

 which none take their source. It must not be overlooked, how- 

 ever, that there is direct evidence to show that in early geo- 

 logical ages, when the continents were small and before the rivers 

 were numerous or large, the waters of the vast ocean of those 

 times were salt. 



The salts of the sea have fed, throughout all time, countless 

 living things which have thronged its water and whose remains 

 now form the rocks of continents or lie spread in beds of unknown 

 thickness over 66,000,000 square miles of the 143,000,000 square 

 miles of the ocean's floor ; they have lent the substance to build 

 the fringing reefs of the land and all the coral islands of the sea, 

 and there are at present, on the basis of an average salinity of 

 three and a half per cent, in the 290,700,000 cubic miles of water 

 which make up the oceans, 90,000,000,000,000,000 tons, or 10,173,000 

 cubic miles, of salt. This is sufficient to cover the areas of all the 

 lands of the earth with a uniform layer of salt to a depth of one 

 thousand feet. 



It seems that the sea was made salt in the beginning as a part 

 of the grand design of the Creator to provide for the system of 

 evolution which has been going on since the creation. Many dis- 

 tinct species of living organisms exist in the sea as a result of its 

 salinity, and tneir remains have largely contributed to the growth 

 of continents. The three great factors in accounting for the sys- 

 tem of currents in the ocean, by which it becomes the great heat 

 distributer of the globe, are changes of temperature, the winds, 

 and salinity. The last mentioned becomes an important factor 

 through the immediate and essential differences of specific grav- 

 ity and consequent differences of level that it produces in dif- 

 ferent parts of the ocean through the action of evaporation and 

 rainfall. 



If, through the fall of rain upon a portion of the ocean or through 

 the action of evaporation in the surrounding parts, the waters of 

 that portion become lighter than the rest down to a certain dis- 

 tance below the surface, two different kinds of motion will imme- 



