THE CHEMICAL PROCESSES OF SOIL FORMATION. 37 



of shellfish, corals, etc. Least in amount of the metallic elements 

 mentioned is potassium. Calculating the total amounts of chlorin, we 

 find that it exceeds in weight any one other element present in the salts 

 of sea-water, being two-sevenths of the whole solids. 



Substantially the same result, with variations due to local causes, as 

 exemplified in the varying composition of river and drain waters, is 

 obtained when we consider the saline ingredients of lakes having no 

 outlet, and in which therefore, the leachings of the tributary land area 

 have accumulated for ages. The Great Salt Lake of Utah, the land- 

 locked lakes of the Nevada basin, of California, Oregon, and of the 

 deserts of Asia, Africa, and Australia, all tell the same tale, which may 

 be summarized in the statement that the chlorids of sodium and 

 magnesium, and the sulfates of sodium, magnesium and calcium con- 

 stitute the bulk of the leachings of the land ; while of other substances 

 potassium alone is present in relatively considerable amount. 



While the above analysis shows the ingredients of sea-water so far as 

 they can at present be directly determined by chemical analysis, yet the 

 presence of many others is demonstrable, directly or indirectly, from 

 various sources. One is, the mother-waters from the making of sea-salt, 

 in which such substances accumulate so as to become ascertainable by 

 chemical means, and even become industrially available in the cases of 

 potash and bromin. Another is the ash of seaweeds, which is in- 

 disputably derived from the sea-water, and contains, among other sub- 

 stances not directly demonstrable in the original water, notable quantities 

 of iodin (of which this ash is a commercial source), iron, manganese, 

 and phosphoric acid. Again, the copper sheathing of vessels, as it is 

 gradually corroded, becomes more or less rich in silver, manifestly 

 thrown down from the sea-water, and the silver so obtained is associated 

 with minute amounts of gold. Copper, lithium, and fluorin likewise 

 have been found in sea water ; and it is probable that close search 

 would detect very many of the other chemical elements as ordinary in- 

 gredients in minute amounts. This is what must be expected from the 

 fact that few mineral substances known to us are entirely insoluble in 

 pure water, and still fewer in water charged with carbonic acid. The 

 latter is always present in sea-water and holds the lime carbonate in 

 solution ; on evaporation or boiling, this substance is the first to be 

 precipitated ; and thin sheets of limestone from this source are com- 

 monly found at the base of rock-salt beds, which, themselves, are 

 evidently the result of the evaporation of segregated bodies of sea-water 

 in past geological ages. 



