156 



NATURE AND PROPERTIES OF SOILS 



trol the hygroscopicity. The following figures from Briggs 

 and Schantz, 1 by whom the hygroscopic coefficient was deter- 

 mined by exposing air-dry soil at 20° C. to a saturated atmo- 

 sphere and then drying at 110° C, illustrate this point. The 

 organic matter was not a serious disturbing factor. 



Table XXIX 



HYGROSCOPIC CAPACITY OF VARIOUS SOILS EXPRESSED IN PER- 

 CENTAGE BASED ON DRY SOIL 2 



Soils 



Coarse sand .... 



Fine sand 



Sandy loam 

 Fine sandy loam 



Loam 



Clay loam 



Clay 



Griggs, L. J., and Schantz, H. L., The Wilting Coefficient for Dif- 

 ferent Plants and Its Indirect Determination; U. S. Dept. Agr., Bur. 

 Plant Ind., Bui. 230, p. 65, Feb., 1912. See also, Loughridge, K, H., 

 Investigations in Soils Physics; Calif. Agr. Exp. Sta., Kep. of Work of 

 the Agr. Exp. Stations of Calif, for 1892-3-4, pp. 76-77. Amnion, Georg., 

 Vntersuchungen uber das Condensationsvermogen der Bodenconstituenten 

 fur Gase; Forsch. a. d. Gebiete d. Agri.-Physik., Band II, Seite 1-46, 1879. 

 Dobeneck, A. F., von, Vntersuchungen uber das Absorptionsvermogen 

 und die Uygroskopizitat der Bodenkonstituenten ; Forsch. a. d. Gebiete 

 d. Agri.-Physik., Band XV, Seite 163-228, 1892. 



'During the many years of soil investigation, especially where the 

 problems had to deal either directly or indirectly with moisture, five 

 methods of water expression have been evolved, their use depending on 

 the nature of the work and on the points to be expressed. They may be 

 listed under two general heads: 



A. Percentage expression 



1. Percentage on a dry basis 



2. Percentage on a wet basis 



B. Volume expression 



1. Cubic inches to the cubic foot of soil 



2. Percentage by volume 



3. Surface inches 



A soil carrying 25 per cent, of water on the dry soil basis contains 20 

 per cent, on the moist basis (soil plus water). The former method is 



