32 
Bulletin 72. 
§ 89. The analyses of the waters from the wells agree with 
the one given in showing that the total solids in the ground water 
contain more calcic sulfate than the incrustations, but much less- 
than the water-soluble portions of the soils, whether it is of the first 
or second two inches. The results of the analyses of other samples 
also agree relative to the magnesic sulfate, viz.: that there is almost 
as much in the water residues as there is in the incrustation or in 
the first two inches of the soil C, and more than in any of the other 
seven water-soluble portions examined. 
§ 90. The most marked difference is shown in the case of the 
sodic sulfate, which makes up 53 per cent, of the alkali incrusta¬ 
tion, 17 per cent, of the solids dissolved in the ground water, 10 
per cent, of the water-soluble in the first two inches of the soil, and 
is absent in the second two inches. The analyses given above do 
not stand alone in indicating this difference, but many analyses, all 
that we have made of the ground waters and three other soil sam¬ 
ples, indicate this to be a fact. Sodic sulfate is always a constituent 
of the total solids in the ground waters, varying in quantity from 
less than 5 per cent, to 23 per cent. I may state here, as an un¬ 
looked-for result, that this salt almost disappears from the drain 
water coming from this area. 
§ 91. The appearance of these two salts, sodic and magnesic 
sulfates, in the incrustations, seems very reasonable if the sugges¬ 
tion made in Bulletin 65, that the incrustation is formed by an 
approximate separation of these efflorescent salts from the more 
permanent ones, especially calcic sulfate, at the contact of the water 
surface with the air, is correct. The suggestion of the formation of 
a double magnesic sodic sulfate lies near at hand in this case, but 
whatever the case may be, we are not justified by the ratio of the 
magnesic salt to the sodic salt in assuming its formation; besides 
there is no urgent need of it, as the deportment of these two sulfates- 
toward the air surface is sufficiently different from that of calcic 
sulfate to permit of the separation as observed. The formation of 
these incrustations is very different from the simple evaporation of 
a solution of different salts to dryness, for these efflorescent salts are 
removed from the solution and its former status is changed. 
§ 92. Why the sodic sulfate forms so small a percentage of 
the water-soluble portion of the soil is not easily explained. That 
it should sometimes be found in the upper portions of the soil in 
large quantities is to be expected, even if as a rule it were present 
in small quantities only or entirely absent, for the tendency is to a 
separation of it on the surface, whence it may be carried back into- 
the soil by rain or abundant atmospheric moisture, being retained 
within the surface layers ©f the soil in which it may form a large 
percentage of the water-soluble portion. We have one instance in 
