44 
Bulletin 72. 
with the soil. No account has been taken of the amount of water 
evaporated, which was probably a larger fraction of the water ap¬ 
plied than we would think, possibly not less than a sixteenth of it. 
The rate of evaporation from a standard tank at the time this irri¬ 
gation was made was 6 inches in 30 days, and as our irrigation 
extended over 3 days, the evaporation probably amounted to fully 
.6 of an inch. 
It required about 34 hours for the water to flow the length 
of the plot, 600 feet, and produce an off-flow. The first samples 
of the off-flowing water were taken soon after the off-flow began, 
and the second samples were taken 8J hours later. At this time 
the off-flow was estimated to be about half of the on-flow. 
§ 127. The albumenoidal ammonia in the ground water was 
materially increased in two of the wells, but in the other two wells 
its amount was affected in a very much less degree. The off-flowing 
water was only slightly richer in this kind of ammonia than the on- 
flowing water. 
§ 128. The rate at which the water flowed over the ground 
and also the rate at which it passed into the soil probably exerted 
an influence upon the amount and kinds of salts taken into solution. 
An attempt was made to determine the rate at which the wells filled; 
they were measured, pumped down, remeasured, and the time noted 
which was required for them to fill again. The rate varied with 
the soil and other conditions, but our results indicated an inflow of 
from 7 to 11 cubic inches ner minute, the water outside of the wells 
standing from 24 to 36 inches above the surface at the beginning of 
the experiment. This does not indicate so rapid a draining out of 
the water from a comparatively free surface as I expected. The 
surface varied in the different wells, but this requires nearly 30 
square inches to furnish one cubic inch of water per minute, or a 
square foot yielded at the rate of 4.8 cubic inches per minute. No 
attempt was made in this crude experiment to find out how much 
space about the well was affected by the lowering of the water in 
the well; it was very small at best. This rate of inflow would 
have diminished materially after a short time. I have elsewhere 
stated that the lateral movement of the solutions, which may be quite 
equivalent to water, is very small, if not zero, in this plot, for the 
amount and kinds of salts in the water in wells near to one another 
are different and maintain their individuality throughout a series 
of changes in the conditions of the ground water, including the ef¬ 
fects of irrigation. The rate of the flow into the wells does not seem 
to be sufficiently high to disturb the relation of the well water to 
Ihe ground water to such an extent as to demand special considera¬ 
tion. The differences between the ground waters and aqueous ex¬ 
tracts of the soil already noted are not sensibly affected by the lat- 
