COLORADO IRRIGATION WATERS AND THEIR CHANGES. 73 
large, sometimes predominating quantities, in the effloresced alkalies, but 
I have no other observed fact to support it. 
37. The very large quantity of magnesic sulfate present may also 
be accounted for by supposing that the ground water, under the then 
obtaining conditions, actually dissolved larger quantities of this salt out 
of the soil than of the others. 
38. It is not clear from any facts which I was able to discover, to 
which of these conditions, if to any of them, the observed fact ought to 
be attributed; to the accumulation of the magnesic salt in the upper 
portion of the soil, due to evaporation from the surface and the conse¬ 
quent action of capillarity, to low temperature, to the abundant supply 
of water over a large area, or to some other unrecognized cause. 
39 The fact is simply this, that the salts in the ground water are 
essentially the same at all times, and the application of water to the 
surface, whether it be irrigation water or rainfall, does not change in 
any material way the salts present. The relative quantities in which 
they are held in solution in the ground water varies quite widely, while 
the causes of the variations are not evident. It is not probable, for in¬ 
stance, that the quantity of magnesic sulfate in the soil experimented 
with, predominates at any time over the calcic sulfate, as the relative 
quantities of these salts found in the ground water in the spring of 1900 
might be held to suggest. The solution obtained by thoroughly exhaust¬ 
ing this soil with water, shows that there is from two to three times as 
much calcic as magnesic sulfate in the top four inches of it. The total 
lime contained in this soil, as shown by analysis of the whole soil, is in 
round uumbers, double that of the magnesia. The lime in the hydro¬ 
chloric extract of this soil usually exceeds the magnesia; in the subsoil 
it is even eight times as great. 
40. The ground waters, under ordinary conditions, always contain 
more calcic than magnesic sulfate, but under the conditions prevailng 
during the spring of 1900, we find the rule reversed—see analyses 
XXXVI, XXXVII and XXXVIII. The cause, or causes, of this were 
evidently not permanent, for within a period of eight days we observe a 
change, in which the ratio of magnesic to calcic sulfate, in the water of 
well A, falls from 2: l to 1.2:1, a ratio which had already been found for 
these salts immediately after irrigation. In the drain water taken on the 
same date, April 2<», 1900, we observe the usual ratio between these salts. 
The drain water is at all times different from the ground water, and too 
much stress should not be placed upon the ratio of these salts observed 
in it. Its chief value, in this case, is to show that, though the condi¬ 
tions in regard to temperature, water supply, etc., were general, they 
have produced no noticeable effect upon the kind or relative quantities 
of the salts carried in the drain water. 
41. The water of well A, on April 9, 1900, was intermediate in the 
character of the salts held in solution between the alkali-incrustations 
forming on this soil, under favorable conditions, and the water usually 
present in the well. It differed from the former in having less sodic sul¬ 
fate, and from the latter in carrying less calcic sulfate and very much 
more magnesic and sodic sulfates. These facts do not seem to be in 
any way dependent upon the solubilities of the salts themselves, nor 
upon any known state of hydration. 
42. The quantities of potash involved were not large, being 15.1 and 
19.2 pounds respectively, for the two seasons, 1898 and 1899. These 
quantities are extremely small, when we consider the mass of other 
salts which was brought into solution. In 1898 we have nearly 2.25 tons, 
in 1899, 2.5 tons of salts brought into solution, and this on plainly too 
conservative an sstimate, while only these small quantities of potash are 
carried along with them. If we were to treat an equal amount of ground 
granite with this amount of water, it would dissolve out more potash 
than is here shown to have gone into solution, notwithstanding the ten¬ 
dency of such a large quantity of salts, 2.5 tons, to carry others into 
olution. This is entirely in accord with facts observed long 
