EXPERIMENT STATION BULLETINS. 555 



of surface tension and viscosity. They have led to the conclusion that 

 the capillary movement of water in moist soils is not controlled entirely 

 by the curvature of the capillary films, as is generally believed, but also 

 by the unsatisfied attractive forces of the .soil for water, 



' (2) When a moist column of soil is kept at 20° and 40° C. and a 

 dry column of soil at 0° C. for eight hours, and tlie two columns are 

 separated by an air space, the percentage of moisture distilled over from 

 the moist and warm column to the dry and cold column of soil is very 

 insignificant for both amplitudes of temperature, and about the same for 

 all moisture contents. 



These results lead to the conclusion (a) that Ihe amount of water lost 

 from the soil by water vapor is very small, (b) that there is no rising of 

 vapor during the night from the warmer soil below to the cold soil above, 

 and (c) that the source of Avater of the dew is not derived from the soil 

 vapor, as is commonly believed. 



(3) When a moist column of soil is in contact with a dry column of 

 soil and the former is kept at 20° and 40° C. and the latter at 0° C. 

 for eight hours, the amount of moisture moved from the moist and warm 

 soil to the dry and cold soil increases with temperature and with mois- 

 ture content. But when the moist column of soil is maintained at 0° C, 

 and the dry column of soil at 20° and 40° C, for the same number of 

 hours, there is very little, if any, movement of water from the former to 

 the latter. 



These results have led to the conclusion that temperature has a very 

 marked influence on the conservation of moisture by mulches, 



(4) No thermo-osmotic phenomena were observed in soils. 



(5) The research on the effect of temperature on the rate of perco- 

 lation of water in soils shows that in the case of sandy loam, silt loam, 

 clay loam, clay and muck the rate of flow increases with rise in tempera- 

 ture up to about 30° C. and then decreases with further rise in tempera- 

 ture. In the case of sand, however, the rate of flow increases with a con- 

 stantly rising of temperature. In the foi'uier soils the results are explained 

 und6r the hypothesis that the colloidal material present swells with in- 

 crease in temperature and tends to close the channels through which the 

 water flowed, 



(6) The water holding capacity of soils, decreased with rise in tem- 

 perature, but this decrease is not due entirely to the diminished surface 

 tension of the soil water but also to other factors. 



(7) The rate of flow of air through soils decreases with rise in tem- 

 perature. This dimunition is not entirely due to the increased viscosity 

 of the gases, but in addition to some changes which the temperature pro- 

 duces in the soil, 



(8) Temperature has a tremendous influence upon the aeration of 

 soils. This influence is not due merely to the expansion of gases of the 

 soil, as is commonly believed, but also to the absorption of gases by the 

 soil at diflerent temperatures, and to the aqueous vapor. 



