SOILS. 



703 



SOILS. 



On the movement of -water in the soil, Mooiimann [ScMlUngh 

 Jour, fiir GasheleHchtHiig und Wasscrversorgung, 1891 ; ahs. in Forsch. 

 Gel), agr. Phys., 17 {189i), JSFo. 5, pp. 449, 450). — The principal point 

 bronght out in this paper is that in all soils water forms hydrates 

 (termed by Graham and Mendelejeff hydrosols) which more or less 

 completely fill up the soil i)ores and interfere with the circulation of 

 water. 



The fact that wet sand molded by the hand retains its shaj^e after 

 drying is an evidence that the water has developed a binding power 

 which the sand did not previously possess. This can be explained in 

 case of pure sand, it is claimed, only by the formation of a tliiu coating 

 of hydrate of silica which binds the particles togetlier. The finer the 

 sand the greater the amount of this hydrate formed. 



While this formation of hydrates in sand lessens the friction between 

 particles and causes them to occupy less space, in case of close-grained 

 dry clay it is so great that the clay increases in volume almost 15 per 

 cent in absorbing the ordinary amount of soil moisture. 



In support of the theory that water combines chemically with clay 

 soils it is pointed out that moderately moist clay yields no water on 

 pressure, and that moistening of clay generates an appreciable amount 

 of heat and develops a j)eculiar odor, at the same time evolving gases. 

 The influence that this formation of hydrates has on the circulation of 

 the water of the soil depends, of course, uj>on the fineness of the soil 

 l)articles and the amount of hydrates formed. 



Soil temperatures, W. Frear and W. S. Sweetsbr {Pennsylvania 

 Sta. Bpt. 1893, pp. 174-181, 187, 223-246).— K record is given of tri-daily 

 observations during 1893 with thermometers at the surface and at 

 depths of from 1 to 21 in. 



The following is a summary of observations during the growing 

 season : 



Soil temperatures, April to September, 1893. 



Analyses of soils, H. Snyder {Minnesota Sta. Ept. 1893, pp. 254- 

 258). — Analyses of 17 samples in addition to those reported in Bulletin 

 30 of the station (E. S. R., 5, p. 857) are tabulated and briefly discussed. 



