118 BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 
by M', and the excess over wilting coefficient by K, then in these 
diagrams the condition is represented by 
M'=WC+K 
rather than 
since it is readily seen that the osmotic equivalents are not propor- 
tionate to the coefficients. 
Table 6. — Osmotic equivalent of soils, in presence of solution at 20 atmos- 
pheres, after four months exposure and other related properties. 
Station. 
Depth. 
Moisture T 
Capillary equiva- ^Jj£g 
moisture. lent, 
100-G. 
coeffi- 
cient. 
Osmotic 
equiva- 
lent. 
I 5SF Cha ?« eta 
Sent. transfer « 
Feet. 
r-i. 
Well sand. 
At, of 3... 
Per cent. 
11.64 
10.00 
10.96 
22.08 
Per cent. 
4.29 
3.60 
4.34 
8.25 
Per cent. 
2.31 
.93 
.76 
2.13 
Per cent. 
11.19 
8. 7 
8.92 
110.06 
Per cent. 
8.88 
7.34 
8.16 
7.93 
8.13 
F-2. 
Well sand. 
lAv. of 3... 
11.34 
16.08 
14.84 
24.70 
5.41 
5.91 
5.86 
9.29 
1.16 
2.63 
2.67 
3.67 
7.84 
8.69 
9.58 
6.91 
6.20 
6.55 
Grams. 
+0.01 
-2.39 
-2.35 
1-0.72 
-1.58 
F-ll. 
Well sand. 
lAv. of 3... 
23.53 
24.00 
18.86 
21.61 
13. 45 
16.25 
11.62 
6.67 
4.72 
3.65 
2.99 
11.06 
10.72 
10.24 
9.90 
6.34 
7.07 
7.25 
9.14 
6.89 
-2.62 
-2.20 
-1.67 
1-1.24 
-2.16 
-1.90 
-1.80 
-2.11 
-1.29 
-1.94 
i Average of 4 samples taken from each well, representing the surface and depths of 1, 2, and 3 feet, so that 
mean value should be equivalent to that of soil as placed in the well. 
1 Approximate. Test made on coarse sandy soil from depth of 4 feet, most nearly approaching the quality 
of sand used in the well. 
Table 6 shows that K varies as between different groups of samples 
from different sources, but that within a group of similar origin K 
is essentially a constant. Thus, it has an average value of 8.13 per 
cent for one group, 6.55 per cent for another, and 6.89 per cent for the 
third, and this value seems not to have any constant relation to the 
change which occurred in the samples during their period of ex- 
posure, so that it may be accepted as representing something near a 
final condition. In one sample representing a limestone soil, K is 
found to be 17.12—15.33 per cent, or 1.79 per cent. In another soil 
of lava origin, containing less of silt and clay, but a considerable 
amount of sodium bicarbonate, K is found to be 12.23—1.11 per 
cent, or 7.79 per cent. 
These findings compel the following conclusions : 
1. The wilting coefficient of a given soil is probably dependent 
both on the solutes present and upon the colloids capable of ad- 
sorbing both the solutes and the water, but more particularly upon 
the latter ; since only very rarely will the solutes be so abundant as 
to create an excessively strong solution before the disappearance of 
the free water. 
