bulletin 82. 
72 
water. The first water that flowed off gave much higher results, but 
subsequent samples showed a rapid falling off. 
29. The water entering the soil caused the solution of not less than 
4,400 pounds of salts per acre-foot, and probably very nearly three times 
this amount. ' 
30. The salts taken into solution by the water entering the soil and 
becoming ground water, are calcic,magnesic and sodic sulfates. The salts 
dissolved in the next largest quantities were sodic chlorid and sodic car¬ 
bonate. 
31. The amount of salts brought into solution in the ground water, 
due to the application of water to the surface, varies not only in the 
total amount of salts, but also in the relative quantities of the individual 
salts. The salt that went into solution the most freely in 1893, that is, 
the salt that showed the largest increase in the ground water, due to the 
irrigation of the plot with which we were experimenting, was sodic sul¬ 
fate, for which we found an increase of 1,430 pounds in each acre-foot of 
ground water. In 1899, the largest increase was shown by calcic sulfate, 
an increase of 1,638 pounds per acre foot. 
32. In 1898 there were two causes which may have contributed to 
bringingaboutthe relatively large increase of the sodic sulfate. One was 
the scanty supply of water, which did not enable us to fill the soil with 
water to the same extent that we did in 1899, so that the relative mass 
of water to that of the soil, or to the salts in the soil, was not the same. 
This is an important condition and one, for the effect of which we have 
no measure. The other was the necessity that we were under of exclud¬ 
ing the water of well D. from our consideration of the results of this 
irrigation, because of an accident. The results shown by this well sub¬ 
sequently indicate that it would have showed a greater increase in the 
amount of calcic sulfate than the other three, and would consequently 
have reduced the relative increase of sodic sulfate. The general results 
were slightly influenced by this omission. Still, after all due allowance 
for these facts has been made, there remains a decided difference in 
the results of these two experiments, one in 1898, the other in 1899. 
33. The character and supply of the water exert an influence upon 
the relative quantities of the salts that go into solution, but there are 
evidently other factors that influence these ratios. The general condi¬ 
tions of the soil, the temperature and the season of the year, including 
all the meteorological conditions, probably have a great influence upon 
the salts in the soil, and the relative quantities of them in solution in 
the ground water. 
34. The effect of a long continued rain in the spring of 1900, when 
the temperature of the water entering the soil was not far from zero, as 
the ground was covered with melting snow, is given in Tables XXXVI, 
XXXVII and XXXVIII. The salt present at this time, April 9, 1900, in 
well A, in the largest quantity, was magnesic sulfate. The quantity of 
this salt present, on this date, was between four and five times greater 
than the average quantity present during the season of 1898. The quan¬ 
tities of calcic and sodic sulfates were also greater than their respective 
average quantities for the same time; that of calcic sulfate was one- 
third higher, while that of sodic sulfate was between five and six times 
greater. The increase of the sodic sulfate over its average quantity for 
1898, is greater than that of the magnesic sulfate, but the amount of the 
former salt present is just a little more than one-half that of the latter. 
3 >. The following general conditions may have contributed in bring¬ 
ing about these variations. The weather during the preceding weeks, or 
even months, also the abundant supply of water simultaneously over a 
large area. I conceive this last condition to differ very greatly from the 
application of even a copious irrigation applied to a limited area of soil. 
36 It is a common observation that the alkali salts effloresce freely 
during the winter season. It may have been the case in this instance 
that an unusual amount of this sait, magnesic sulfate, had accumulated 
in the upper portions of the soil, owing to evaporation during the pre¬ 
ceding winter. Such a result is suggested by the presence of this salt in 
