20 BULLETIN 1221, U. S. DEPARTMENT OF AGRICULTURE. 
While but 3 tubes inclined downward from the horizontal are 
included, some 24 tubes were used. To have included more would 
have added materially to the length of this report without adding 
correspondingly to its value, since information secured from the other 
tubes is similar to that presented above and differs only in degree or 
as influenced by methods. 
In considering tubes Nos. 21, 22, and 23, it must be kept in mind 
that in tube No. 21 the moisture had reached the lower end of the 
inclined column and that water was dripping from the lower end 
when the samples were taken. In the other two tubes the moisture 
had not reached the lower end of the columns, and there was dry soil 
below and in contact with the lower extremity of the wet soil. In — 
these last two tubes two forces tended to draw the moisture down- 
ward in the inclined part of the tube at the time the samples were 
taken, a capillary force and the force of gravity, while in tube No. 21 
there was only the force of gravity acting at the lower end of the soil 
column. 
Referring to Table 8 and Figure 7, it is found that in tube No. 21 
aang 
~., 
COPE 
LET Trupeat | fy er | | 
“Dees (bd aie sepeeeer! bal alc 
20 3 40 50 
Inches Down 
Fig. 7—Distribution of moisture in columns inclined downward. 
of Mo/sture 
(3 
Percentag 
co 
there is a very uniform percentage of moisture from the upper end of 
the inclined part of the soil column to within about 15 shes of the 
lower end of the soil column. From the fortieth to the fifty-eighth 
inch there is an increase in the moisture percentage and the greatest 
percentage of moisture in the entire soil column is nearly at the lower 
end of the inclined part of the column. The distribution of moisture 
in the 15 inches of the column nearest the apex is somewhat similar 
to that found in the vertical soil columns. At the lower end the 
absence of any capillary action below the wetted area causes a piling 
up of the moisture. The uniform distribution of moisture by per- 
centage in the first 40 inches of the inclined soil column is significant 
in considering the distribution of moisture in the field under irrigation, 
as 1t would indicate that there is a maximum or optimum percentage 
of moisture that can be retained within the soil and that this opti- 
mum is not comparable to capillary saturation or many of the other 
terms of measure now in use by the soil physicists. 
In tubes Nos. 22 and 23 the samples were taken while the moisture 
was still moving downward within the soil column, showing a dis- 
tribution of moisture differing materially from that shown in tube 
No. 21. In these tubes the maximum percentage of moisture is 
near the upper end of the column and the minimum moisture content 
at the lower end. The decrease in the percentage of moisture from 
the top to near the bottom of the column is rather uniform for both 
these soils. This distribution of moisture would be somewhat com- 
parable to the distribution found in a field under irrigation where 
