1621 
ee Ca ; 
eq. ——_—-__ = 0,525 
Na+ Mg+Ca 
and for normal salt water (sea-water) 
N 
eq. — Ë 0,787 
Na + Mg Ca 
M 
eq. — 8 OS 
Na+ Me +Ca 
TE 
Na + Mg +Ca 
Hence, near the transition zône where the concentration of the 
chlorine ions and that of eq. Na + Mg + Ca are still the same as 
these of the fresh water, the mutual proportion in which Na, Mg 
and Ca are present is already about that of the salt water. 
We may, therefore, imagine that in the normal fresh water 
— near the border to salt water — an exchange has taken place 
between equivalent quantities of Na, Mg and Ca and chiefly in such 
a way that Ca has been removed from the water and Na has been 
introduced. 
The phenomenon might be explained as follows in connexion 
with the way in which the fresh water has arrived into the sub- 
soil. The sand of the dunes rests on an old sea bottom and before 
the formation of the dunes this local land was submerged by the 
sea. The soil might then have been permeated by sea-water to a 
great depth. 
Since the formation of dunes thereon precipitant water has pene- 
trated into the soil and displaced the salt water. 
Where fresh water is found now, there has consequently formerly 
been salt water. The normal fresh water must then be looked 
upon as the penetrated precipitant water which contains carbon 
dioxide and has in consequence dissolved calcium carbonate from 
the shells present in the soil. 
The normal salt water is the sea-water still present. If in the 
soil are present solid substances such as amorphous silicates of 
aluminium with sodium, magnesium or calcium, or may be alumi- 
nium silicates which like the zeolithes possess the power, v hen in 
contact with a solution of salts, of mutually exchanging the last 
three elements, the said phenomenon might occur. 
So long as the soil was still permeated by water in which Na, 
Mg and Ca were dissolved in about the proportion in which they 
occur in sea-water, and particularly if this water circulated and 
1045 
