8 
Bulletin 72. 
already mentioned. Water was turned into the ditch late in the 
afternoon of April 20th. By 6:15 p. m. of the 23d the water 
plane had risen 0.31 of a foot in well A, and 0.30 of a foot in 
well G, the former being 130J feet and the latter 142J feet distant 
from and west of the ditch. No rain had fallen during the preceding 
17 days, and the effect observed was probably wholly due to the 
influence of the ditch, and it is doubtful whether the effect of the 
ditch upon the height of the water plane was ever much greater 
than is here indicated, 0.30 of a foot. 
§ 17. The total solids and the chlorin present in the water 
before and after the rise showed a decrease. If the rise were due 
to unfiltered water passing in from the surface, or even near it, 
as from the bottom of the ditch, this result would stand alone 
and in contradiction to the results observed when the level of the 
water had been raised by a copious rainfall or by the application 
of irrigation water. In both of these cases the total solids and the 
chlorin were greatly increased, but not in any definite ratio—the 
increase in the amount of chlorin being more rapid than that of 
the total solids. 
§ 18. The decrease in the total solids held in solution sug¬ 
gests the damming hack of the underground water and a rising of 
water which was usually below the clayey stratum. The princi¬ 
pal fact on which this interpretation rests is that the water taken 
from below this stratum was actually poorer in total solids than 
the water above it. We also attempted to study the effect of a 
drain run for the most part just outside of and south of the plot, 
but owing to a variety of causes, the principal one of which was 
our inability to properly attend to it, this experiment was aban¬ 
doned. 
§ 19. When the water table in this plot had been raised by 
irrigation it required from 10 to 13 days for it to fall to the level 
at which it stood before irrigation. The rate at which it fell was 
very nearly the same throughout the plot and did not reach this 
level at the west or higher end first and gradually proceed east¬ 
ward as it would do if there were sufficient freedom of flow and 
the drainage was from the east end of the plot. 
§ 20. It is mentioned on a preceding page that when the 
water level rose owing to the change in the conditions of capillarity 
caused by a slight rainfall, it required only about three days for 
it to recede to its former level, while we state that after an irriga¬ 
tion it required from 10 to 13 days. The two cases are quite dif¬ 
ferent. In the latter case we have displaced the air and filled the 
soil with water, piling it up on the existing water plane; in the for- 
