538 STATE BOARD OF AGRICULTURE. 



A portion of the tcatcr that left the soil at the various temperatures 

 should he attributed to the decreased adhesive poiver of the soil for water. 

 It is not proper to consider the soil mass itself, as has hecii done here- 

 tofore, as a static and passive skeleton, and as heing unaffected dij, and 

 irresponsive to temperature, and as playing no part in the capillary 

 movement of ivater ichen it is moist. Indeed, the physical properties of 

 the solid soil are affected hy temperature as well as those of the liquid, 

 for hoth classes of matter obey the law of Jcinetio energy of matter. It 

 is ivrong to speak then of the water-holding poicer of a soil being de- 

 creased by rise in temperature because the surface tension of its water 

 is decreased ; or that water is pulled upivard in a moist soil because only 

 of the curvature of the capillary films. 



In view of these considerations, it might be concluded that the diminu- 

 tion of the water holding capacity of a soil due solely to the decreased 

 surface tension of the soil water by temperature is insignificant. 



EFFECT OF TEMPERATURE ON THE RATE OF FLOW OF AIR IN 



SOILS. 



Unlike liquids, the viscosity of gases increases with rise in tempera- 

 ture. The velocity of flow of air in soils, therefore, with rise of tempera- 

 ture, should diminish correspondingly. The experiments of Ammon^" 

 and Wollney-^ have confirmed this conclusion. Amnion has also shown 

 that the actual and calculated results agree. Both of these investiga- 

 tors, however, obtained their results under too abnormal and unnatural 

 conditions, in that they used only dry powdered soils. The foregoing in- 

 vestigation on the velocity of flow of water through soils at the higher 

 temperatures, gave occasion to suspect that the passage of air in dry 

 soils may not be the same in moist soils either in order or magnitude. 

 For this reason, the research presented herewith was undertaken. 



The method of procedure consisted of drawing air through a moist 

 column of soil at different temperatures by means of a small tank aspira- 

 tor. The column of soil was contained in a tube, shown in figure 9, which 

 is 8 inches long, and 8 inches in diameter, and has a small opening at the 

 bottom for forming connections with the aspirator. This soil tube was 

 surrounded by a circular compartment which served as a temperature 

 bath. The soil column was about 5.7 inches high. In order to obtain 

 as uniform conditions of structure and compactness among the different 

 soils as possible, they were placed in the tube in air dry condition, 

 slightly tapped, and water allowed to percolate through them for sev- 

 eral days. Following this treatment they were subjected to an alternate 

 drying, wetting, freezing, and thawing. These processes tended to give 

 them a textural and structural condition somewhat similar to that usu- 

 ally found in natural soils under field conditions. The soils were used for 

 the experiment when they contained, what is considered, an average mois- 

 ture content. As they lost their excess of water the colloidal types con- 

 tracted in mass and left a space between the sides of the column and the 

 inner wall of the tube. This space was filled with hot paraffin so that 



soForch, a. d. G. D. Agrik — Physik, Bd. 3, S. 209. 

 "Forch, a. d. G. D. Agrik — Physik, Bd. 16, S. 193-222. 



