Feb. s, 1917 
Measurement of Inactive Moisture in Soil 
217 
The wilting of plants appears to be due mainly to two causes: First, 
to the great force with which the moisture is held by the soil, and, second, 
to the large osmotic pressure of the soil solution at the wilting coefficient. 
The dilatometer method appears to be of considerable value in show-' 
ing (1) that soils cause water to become unfree, as indicated by its re¬ 
fusal to freeze, (2) in measuring quantitatively the amount of water 
thus becoming unfree, (3) in determining, under certain empirical 
conditions, the wilting coefficient of soils, and (4) in classifying, under 
certain empirical conditions, the water in the soil into free, capillary, 
physically adsorbed, and chemically combined. 
The work herein reported should be considered only as preliminary. 
The investigations upon the subject are being continued. 
LITERATURE CITED 
(1) Alway, F. J. 
1913. Studies of the relation of the non-available water of the soil to the hygro¬ 
scopic coefficient. Nebr. Agr. Exp. Sta. Bui. 3, 122 p., 37 fig. 
(2) Bouyoucos, G. J., and McCool, M. M. 
1915. The freezing-point method as a new means of measuring the concentra¬ 
tion of the soil solution directly in the soil. Mich. Agr. Exp. Sta. 
Tech. Bui. 24, 44 p. 
(3) Bouyoucos, G. J. 
1915. Effect of temperature on movement of water vapor and capillary mois¬ 
ture in the soil. In Jour. Agr. Research, v. 5, no. 4, p. 141-172. 
(4) Briggs, L. J., and Shantz, H. L. 
1912. The wilting coefficient for different plants and its indirect determination. 
U. S. Dept. Agr. Bur. Plant Indus. Bui. 230, 83 p., 9 fig., 2 pi. 
(5) Foots, H. W., and Saxton, Blair. 
1916. The effect of freezing on certain inorganic hydrogels. In Jour. Amer. 
Chem. Soc., v. 38, no. 3, p. 588-609,13 fig. 
(6) Jones, H. C. 
1914. The Elements of Physical Chemistry, ed. 4, 650 p., 78 fig. New York. 
(7) Kosaroff, P. 
1897. Einfluss verschiedener ausserer Factoren auf die Wasseraufnahme der 
Pflanzen. 64 p. Leipzig. 
Cited by Jost (Jost, Ludwig. Lectures on Plant Physiology. 
Transl. by R. J. Harvey Gibson, p. 32. Oxford [Eng.], 1907). 
(8) Muntz, A., and Gaudechon, H. 
1909. Les d6gagements de chaleur qui se produisent au contact de la terre s&che 
et de l'eau. In Ann. Sci. Agron., s. 3, ann. 4, t. 2, fasc. 6, p. 393-443, 
5 
(9) Shuix, C. A. 
1916. Measurement of the surface forces in soils. In Bot. Gaz., v. 62, no. 1, 
p. 1-31,5 fig. 
