34 
BULLETIN 835 y II. S. DEPARTMENT OF AGRICULTURE. 
served in nearly all of the flumes that less water is required per inch 
about the third day than at any other time. In all cases, however, 
more water was required per inch at the end than was required at the 
beginning of the experiment. It is observed that for soils of the 
heavier type represented in flume 54, for some time after the com- 
mencement of the experiment less wateT is required per inch than 
for the following day ? but after about the thirtieth day there is a 
very rapid increase of the water requirements. It is probable that 
there is some concentration of moisture at the top of the vertical lift 
before the moisture changes direction to the inclined part of the flume 
and that this moisture is partially drawn upon to advance the mois- 
ture in the inclined part of the flume. After a few days this surplus 
supply, if such it may be called, is exhausted and then the moisture 
to advance the wetted area in the flume can be derived only from the 
supply in the tank. It must be kept in mind also that with the lapse 
of time a greater wetted area is exposed to evaporation, and this in 
itself would account for some additional water requirement per inch. 
In some' cases the water requirement per inch at the end of the for- 
tieth clay was about double the requirement the first day, but in the 
heavier soils this is not so pronounced. 
Table 20. — Water used to advance moisture 1 inch at different times, in cubic 
centimeters. 
Number 
of days. 
Hume. 
4 
34 
54 
74 
94 
204 
1 
3 
5 
10 
15 
20 
30 
40 
50 
57 
c. c. 
319 
346 
425 
450 
545 
c. c. 
385 
447 
498 
533 
569 
607 
684 
C. C. 
743 
707 
700 
677 
680 
697 
735 
806 
846 
884 
c.c. 
290 
338 
336 
364 
411 
419 
507 
567 
C.C. 
566 
562 
571 
597 
634 
64T 
724 
c.c. 
311 
360 
1 
FLUMES INCLINED UPWARD FROM THE HORIZONTAL AT AN ANGLE OF 15°o 
To throw some light upon the effect of a relatively small inclina- 
tion of the flumes upward from the horizontal, the data will be given 
and discussed for the flumes inclined upward at an angle of 15° and 
open on top to evaporation. The flumes are the same in every respect 
as the others, except the angle of inclination. In these flumes there 
is a vertical lift of 4 inches before a change is made in the direction 
of the flumes. 
They show a much less movement of the moisture and a much less 
use of water than the horizontal flumes, but a more extended move- 
ment of the moisture and greater use of water than the vertical 
flumes. 
