COLORADO IRRIGATION WATERS AND THEIR CHANGES. 47 
§ 80. The sample of water taken April 9, 1900, well A, just 
before the end of an unusually heavy and protracted rainfall, 
whereby the ground was filled with water, contains in an acre-foot 
of water 28,197 pounds of salts. The water of this well is usual¬ 
ly high, therefore to obtain a better idea of what the actual in¬ 
crease is, I have computed the average amounts of sulfates in this 
water as given for 11 samples taken in 1898. When the water 
was low in this well the total solids were also low. In November, 
1898, there were 164 grains per gallon. 
WATER OF WELL A. 
April 9 , 1900. 
Total solids in an acre-foot_ 28,197 pounds 
Calcic Sulfate_ 4,708 pounds 
Magnesic Sulfate_ 10,179 pounds 
Sodic Sulfate__ 5,639 pounds 
Average for 1898. 
8,899 pounds 
3,115 pounds 
2,492 pounds 
979 pounds 
§ 81. The sample of water, well A, taken eight days later, 
serves to show how rapidly the total solids fell at this time. The 
water plane had in meantime fallen about 0.8 of a foot. The total 
solids in an acre-foot have fallen from 28,197 to 17,722 pounds, a 
difference of about 10,000 pounds. Further, the salts remaining 
in solution have another ratio. On April 9, the calcic to the mag- 
nesic to the sodic sulfate stood roughly as 1 : 2 : 1, but on the 
17th inst. they stood as 1 : 5 : 3^, from which it appears that the 
calcic sulfate has receded to the greatest extent, magnesic sulfate 
next and the sodic sulfate in the least measure. 
§ 82. Well G is near well A but is a shallower well and its 
waters are separated from those in an underlying stratum of gravel 
as explained in a former bulletin. This sample perhaps represents 
the water in the soil more faithfully than does the water of well 
A, but in the main it presents the same general features, the rela¬ 
tive quantity of the salts being a little different and their total 
quantity a little higher. 
§ 83. Other samples of water were taken from these wells 
one month later, when the water plane had fallen 16 inches. These 
samples show 142.5 grains total solids for well A, a decrease of 
582.5 grains; and 379 for well G, a decrease of 91 grains per gal¬ 
lon. The percentage of calcic sulfate had materially increased in 
well A, but only slightly in G; that of the magnesic sulfate was 
about the same, while the percentage of sodic sulfate had decreased 
in each case. 
§ 84. We have more potassic oxid in the water from well G 
than in that from well A. In the latter we have 44.5 pounds, in 
the former 63.6 pounds per acre-foot, neither of them being very 
large quantities; the smaller being scarcely 10 times as much as 
water dissolves from finely divided felspar in a few days. 
§ 85. These experiments indicate that either simple solution 
of salts, feebly held in the soil, takes place on a large scale, or else 
