COLORADO IRRIGATION WATERS AND THEIR CHANGES. 45 
used in this irrigation literally vanishes as a factor in any question 
pertaining to nitrogen. 
§ 77. The nitrates, or rather the corresponding nitric acid 
in the ground water before and after irrigation, does not show 
changes on the scale I anticipated. An acre-foot of ground water 
before irrigation contained 6.413 pounds of nitric acid, as nitrates, 
and after irrigation 9.861 pounds, which correspond roughly to 2.2 
pounds of nitrogen, a wholly insignificant amount from any prac¬ 
tical standpoint. The amount is not only small but it must also 
be considered that at least three and one-half feet of soil have prob¬ 
ably been involved in producing this result. Whatever reactions 
may have taken place, the elimination, or the passing of the 
nitrates into a free solution, has taken place to a very small extent.^ 
§ 78. Nitrous acid is present, both before and after irriga¬ 
tion, in such small quantities that a much more extended and 
careful investigation would be required to justify even a tentative 
interpretation. The quantity present after, is greater than before 
irrigation, but the quantity present in either case is small, not a 
tenth of that present in the ditch water. 
§ 79. In the spring of 1900 we had an exceptionally heavy 
precipitation, snow and rain. Beginning March 27, we had 3.5 
inches of snow; on the 30th, a little rain, and from April 4 to 9 
inclusive, rain or snow daily. During this time we had 12 inches 
of snow fall, and a total of 4.2 inches of water. This differs 
materially from an irrigation of 4.2 inches, the whole surface of 
adjacent land receiving the same amount of water which, I con¬ 
sider, influences the water plane materially, either by movement 
or pressure. The water plane in this case was brought up to 
within a few inches of the surface. This may have been the result 
of water from the adjoining lands. The snow which melted 
slowly, and to which there was a daily addition of from .2 to .4 
inches of rainfall at this time, gave the water opportunity to enter 
the soil slowly and over the whole area at the same time. 
Samples of well A were taken April 9 and 17, 1900, when the 
water plane was perhaps at its highest point, the analysis of which 
resulted as follows: 
