346 Professor J. Jolij — Salt and Geological Time. 



in India might well circulate from the earth to the air, and be 

 returned by the rains to the rivers. Such chlorine is, of course, 

 derived by solvent denudation from the soils. 



Mr. Ackroyd (Chemical News, June 7th, 1901) goes so far as to 

 assume that the inland salt lakes must owe their salts mainly to 

 wind-borne chlorine. That some of the salt lakes of the earth 

 situated near the ocean, or in the track of storms, or even of 

 prevailing winds from the sea, derive contributions of salts from 

 the ocean, is probable. Calculations have been made by Pierre in 

 France and others showing how considerable in amount the salts 

 carried from the sea in immediate coastal regions may be. It is, 

 however, only necessary to refer to the chemical composition of the 

 salt lakes themselves to see that any such origin for the greater 

 mass of the salts present is totally inadmissible. The Dead Sea, 

 for instance, shows a very large excess of magnesium salts over 

 sodium salts, their chlorides constituting 15'9 per cent, and 3'6 per 

 cent, respectively of the total solids. There is even a large excess 

 of calcium over sodium in its waters. In the Great Salt Lake the 

 proportions are just the other way ; the percentages are nearly 

 marine, 11*9 of sodium chloride and very little magnesium chloride, 

 but 1-1 per cent. There is relatively very little calcium. Now 

 this is the more embarrassing for Mr. Ackroyd's hypothesis, in that 

 the first lake is close to the sea, the latter very remote from it. 

 Thus the lake which is most favourably situated for the rain supply 

 of sea-salts is just that one which most completely departs in its 

 chemical composition from that of the ocean. Again, we find a lake 

 such as the Elton Lake of the Kirghis Steppe, 200 miles from the 

 Caspian, possessing a chemical composition approximating to that of 

 the Dead Sea : 19-7 per cent, of Mg 01, 5-3 per cent, of Mg S O4, and 

 3'8 per cent. NaCl. Calcium is, however, in its case absent or 

 inappreciable. Now while the observed wide differences in chemical 

 composition are entirely at variance with a pluvial origin, the rain 

 being supposed to derive its burden from the common reservoir of 

 the ocean (almost homogeneous in composition), they are quite in 

 accord with an origin by solvent denudation, as a glance at the 

 considerable differences of river analyses will show, and as indeed 

 would be a priori inferred from the wide range of solubility and 

 chemical composition of the surface materials of the earth. 



But all indirect arguments as to the magnitude of the error which 

 might arise from the circulation of sea-salt must be used in sub- 

 ordination to a simple demonstration, on the known facts, of the 

 magnitude of the maximum error possible from this source. The 

 estimation of the maximum error is easily arrived at. 



Professor Dittmar in his report on the chemical composition of 

 the ocean shows that the amount of chlorine present is in excess 

 of the sodium, so that attaching chlorine ions to sodium ions there 

 remains over a large excess of chlorine, appearing in the statement 

 of total solids as 10-8 per cent, of Mg CI. We have, in fact, 77-7 

 per cent, of Na CI and 10-8 per cent, of Mg CI. A simple calculation 

 will show that it results that 18 per cent, of the CI must be 



