34 
Bulletin 65. 
kind, sulfates, but while the predominant soluble salt in the soil is 
calcic sulfate, that in the alkali which effloresces from this ground 
is sodic sulfate, with magnesic sulfate second in quantity, while the 
calcic sulfates is but little greater than the sodic chlorid. 
§ 73. The analysis is not unsupported in showing a large 
amount of calcic sulfate to be present. I caused several boxes of 
the soil to be gathered and planted with beet seed. These boxes 
were covered with glass and left standing for some days. When 
they were examined again there was an abundant crop of fine 
acicular crystals of gypsum uniformly distributed over the surface. 
Inspection of the soil as it was turned up by the plow also showed 
this substance to be present. Its abundance suggested the possi¬ 
bility of this soil having sometime received a heavy dressing of 
gypsum, in the hope of correcting the evil of the alkali, but I could 
not learn that such had been the case, and the presence of the gyp¬ 
sum in its present quantity seems to be due to accumulation of this 
salt from the evaporation of the ground water. 
WATER-SOLUBLE PORTION OF THE SOIL DIFFERENT FROM SALTS IN 
GROUND WATER. 
§ 74. The salts held in solution by the ground water agree 
more nearly with the water soluble in the soil than those which 
effloresce and are considered as alkali, but even the ground waters 
are not solutions of the water soluble portion in the soil. They 
differ in two essentials, in the amount of silicic acid and also in that 
of potash, which they contain. The water-soluble portion of the 
soils being richer in these constituents, sometimes containing ten 
times as much of one or the other of these. The water-soluble in 
the soil, on the other hand, is not at all uniform in its relative con¬ 
tent of sodic sulfate, and is oftener poor in this salt than even 
mediumly rich. In only two cases out of the eight following analy¬ 
ses does it constitute any considerable fraction of the water-soluble 
salts, and in these cases its presence in such large quantity, 17.7 
and 27.2 per cent, of the soluble salts, is probably due to its concen¬ 
tration at the surface and its subsequent w r ashing back into the soil, 
as the samples represented the first two inches of the soil from sec¬ 
tions where efflorescences are always formed under favorable condi¬ 
tions. The fact that the water-soluble salts are richer in potash 
than the soil water is explicable by the facts which have been 
demonstrated, by the action of water on the feldspar and the prop¬ 
erty of certain compounds in the soil of exchanging lime for potash 
brought into contact with them through the agency of solutions, 
the ground water being in this manner deprived of its potash, re¬ 
ceiving lime in exchange. The analyses of the parts of the soil 
classified according to the size of their grains showed an increasing 
percentage of potash as the grains of the respective parts became 
