COLORADO IRRIGATION WATERS AND THEIR CHANGES. 53 
ture operates, the amount is trifling. An example will show how 
thoroughly justified is this statement. If our soil contained 0.1 
per cent, of nitrogen and we take two acre-feet of it, it will con¬ 
tain in round numbers 7,000 pounds of nitrogen. It would 
take 1,227 acre-feet of drain water to contain this amount, taking 
all forms of nitrogen existing in the water. The drain water does 
not, unfortunately, represent the water draining from any given 
acre of soil, but that draining from many acres. It is understood 
that the value of such examples is purely illustrative. 
THE RETURN WATERS. 
§ 98. We have considered the Poudre water and seen that it 
suffers little or no change in character so long as it remains in its 
mountain course, but that its character changes rapidly as it enters 
the plains. We have seen that in flowing through the ditches for 
use in direct irrigation it also changes rapidly. (See table XII— 
analysis of ditch water as used for irrigation). We have studied 
the effects of storage upon the amount and character of the salts 
held in solution. (See analysis of waters of Terry lake, Long pond, 
Warren’s and Windsor lakes). We have further endeavored to 
present the manner and extent that its composition is changed by 
flowing over the soil as off-flow water; by entering the soil as 
ground water; by passing through and flowing out of it as drain 
water. 
§ 99. If possessed with the desire to do so, anyone could 
make suggestions which, had they been feasible at the time, or 
perhaps even been seen as they can now be seen, would, if fol¬ 
lowed out, add greatly to the value of this work. From the very 
beginning I desired to make a study of the changes taking place 
upon the application of water for irrigation purposes in a different 
manner, but it was not feasible and I have done the best that I 
could. While I think the results of my experiments in this re¬ 
gard exaggerate some of the relations of the individual results to 
one another, I am not prepared to regret the fact, for I believe that 
the exaggeration serves a good purpose by emphasizing; for in¬ 
stance, the profound manner in which the laws of diffusion are 
modified within the soil, and the tenacity with which the soil par¬ 
ticles retain the molecules of different salts, without in any appre¬ 
ciable way destroying their value, as a presentation of the typical 
reactions which take place. I think that it is true everywhere 
under our conditions that calcic sulfate is permitted to pass with 
comparatively more freedom than sodic sulfate or chlorid. I do 
not know whether this is due to the presence of this salt in quan¬ 
tities approaching the point of saturation of the soil and water, or 
not. With whatever weaknesses and insufficiencies our experi¬ 
ments may be beset, we have placed them upon record and will 
