138 University Geological Survey of Kansas. 
it concentrates the salt crystallizes out. It is evident that the 
mother liquor left after a long run will be rich in the most solu- 
ble salts of the brine. : 
‘“Some observations” have been made on the water of the 
Mediterranean Sea, where it has been noticed that at the Straits 
of Gibraltar there is an undercurrent flowing out and an upper ~ 
current flowing back into the sea. The water of the Mediterra- 
nean contains, in proportion to its salt, 23 times as much MgSO, 
as that of the Atlantic, and this excess is supposed to be in the 
upper levels. It follows therefore that more of the upper lay- 
ers, on concentration, can attain a density that will enable them 
to penetrate below the level of the bar. They will therefore 
glide over the lower zone, and giving way to the ‘feed water’ 
from the Atlantic, will pass out under it into the latter body.”’ 
‘‘If this were applied to the salt and gypsum basins, we see 
that magnesium salts flow out, while gypsum and salt laden 
water flows in. As long as the specific gravity is constant then 
the deposit will be about the same in character. 
‘‘According to Usiglio, sea water, concentrated to one-half its 
volume, deposits a large part of its CaCQO,, but between this 
point and a further concentration to 19 per cent. of its original 
volume only traces of CaCO, deposit. At the latter point how- 
ever another large precipitation of CaCO, takes place. The 
first precipitation begins gradually and ends abruptly, while 
the second precipitation begins abruptly and ends gradually. 
This is supposed to be due to the action of calcium sulphate on 
sodium carbonate. This would be represented by the equation : 
Na,CO,+CaSO,—CaCO,+Na,80,. 
‘‘Tf there is any substance in solution which is deposited be- 
tween the specific gravities of the two degrees of concentration, 
it will lie between the two layers of CaCO,. Since the gypsum 
is more soluble in salt water than in fresh, and since when ocean 
water concentrates double salts may be formed, as well as the 
NaCl, CaCl,, Na,SO,, and CaSO,, the sudden and well marked 
deposits of CaSO, might be due to the sudden dilution of the 
concentrated water, or by the addition to it of a quantity of 
Beh UG, Pewee INL, Top i, 
