30 BULLETIN 835, U. S. DEPAKTMEXT OF AGEICULTUEE. 
A comparison of figure 4 with figure 2 shows very strikingly the 
part gravity plays in capillarity. It shows to what extent gravity 
aids or retards the movement of soil moisture by capillarity. An- 
other striking feature is the comparative uniformity of the rate of 
movement of the moisture after the first three or four days. TThile 
there is a general slowing down of the rate at which moisture ad- 
vances from day to day, it is so much less marked in these flumes 
than in the flumes discussed in previous sections as to be of compara- 
tively little moment. 
It is observed that after the first day or two the type of soil used in 
the flumes is of greater importance in limiting the extent of the move- 
ment of the moisture, The more open and porous the soil, the more 
rapid and extended the movement of the moisture. For instance, in 
the sandy Idaho soil of flume 201, the moisture advanced as far in 
one day as it would in the heavy Eiverside soil in five and one-half 
days and 50 per cent farther in the first day than it would hi the 
heavy TThittier soil- in 30 days. In flume 201 the only limit to the 
extent of the movement of moisture was the ability of the wick to 
furnish the moisture. However, the porosity of the soil is not the 
only factor, but the transporting power of the soil itself is of prime 
importance. For instance, comparing flume 34 (heavy Eiverside) 
with flume 74 (Upland), flume 34 has the greater rate of movement 
of moisture at all times within the limits of the experiment, and yet 
the soil of flume 74 has the greater porosity. The difference in the 
rate of movement in these two soils appears to be due to the difference 
in the capillary power of the wick to transmit the water from the 
tanks to the flumes proper. Had there been less vertical lift from the 
tank to the flume hj the wick, flume 74 would undoubtedly have 
shown the greater rate of moisture movement. The effect of porosity 
is well illustrated in flumes 74 and 94. The soil in flume 94 has the 
greater porosity, and while the rate of movement of the moisture is 
less in this flume for the first week, it has the greater rate of move- 
ment thereafter. Again, comparing flumes 4 and 34. the soil in flume 
4 has the greater porosity, but the soil in flume 34 the greater capil- 
lary power, and after the first two week- the rate of movement of 
moisture in flume 34 is greater. 
In table 17 is given the extent of movement of moisture as shown in 
figure 4, in percentages of the extent of movement in flume 34. 
That i-. in flume 34 the moisture had moved the first day 26 inehe-. 
or 100 per cent. In flume 4 the moisture had moved the first day 
28.85 inches, or, as compared with the movement of moisture in flume 
34, 111 per cent, while in flume 54 the moisture had moved 10.7 
inches, or. based on the movement in flume 34. 41 per cent. Flume 31 
maintained a relativelv hisrher rate of movement of moisture than 
