346 
Journal of Agricultural Research 
Vol. VII, No. 8 
A method which will give results sufficiently reliable and accurate for 
many purposes, such as soil surveys, and yet be far more simple even 
than the preceding and more economical of time where any very large 
number of samples is to be handled, seems capable of development. 
This method would be an indirect one based upon the determination of 
the hygroscopic moisture in air-dried samples. As our work on this was 
interrupted several years ago by the removal from Nebraska first of the 
junior author and later of the senior author and there appears little 
probability of either of them being able to continue the work, at least for 
some time, the results are reported in the hope that in some other labo¬ 
ratory the limitations of the method may soon be determined. 
HISTORICAL REVIEW 
Hilgard’s method for the determination of the maximum water 
capacity first proposed in 1893 (8, p. 256; 9, p. 74) has later been described 
in various publications (12, p. 82; 10, p. 15; n, p. 209). From a com¬ 
parison of the hygroscopic coefficient with the wilting coefficient in the 
case of a series of 17 soils and of the maximum water capacity with the 
wilting coefficient in the case of another series of some 15 soils Briggs 
and Shantz (4) have derived the formula: 
Hygroscopic coefficient = (maximum water capacity— 21) X 0.234 
Unfortunately only four of the samples appear in both series. The 
data on these are reported in Table I. The calculated values agree 
fairly satisfactorily with those directly determined. 
Table .1 .—Relation of the maximum water capacity to the hygroscopic coefficient as found 
by Briggs and Shantz 
Soil No. 
Type of soil. 
Maximum 
water 
capacity. 
Hygroscopic coefficient. 
Difference. 
Determined. 
Calculated. 
7. 
Coarse sand. 
23. 2 
29.9 
o- 5 
5 
0. s 
2 . I 
0. O 
2. 
Fine sand. 
+ .6 
8. 
.do. 
28.5 
31-4 
2. 3 
I* 7 
- .6 
9 . 
2. 3 
2.4 
+ • 1 
Briggs and Shantz appear to have overlooked the work of Eough- 
ridge (12), who, some 20 years previously, using some 40 California 
soils ranging in texture from clays to sands, made a critical study of the 
relation of both the maximum water capacity and the hygroscopic 
coefficient to the mechanical composition. In the case of all of these he 
determined the hygroscopic coefficient, the maximum water capacity, 
both by weight and by volume, and the mechanical composition. In the 
first three columns of Table II we give the portions of his data dealing 
with the present subject, arranging the soils in the order of their hygro- 
