Temperature and Capillary Moisture in Soils 



45 



various moisture contents of the different soils and the percentage of 

 moisture moved from the column of soil at 20° to the column of soil at 

 0° and from the column of soil at 40° to the column of soil at 0°. The 

 percentage of moisture moved represents the difference between the 

 percentages of moisture found in the cold and the warm columns of soils, 

 respectively, at the end of the experiment; at the beginning of the 

 experiment the moisture content was the same in both columns of soil. 

 Figure 3 represents these data in a graphical form. 



Table II. — Movement of ynoisture frovi a ivartn to a cold column of soil of uniform 

 moisture content 



The foregoing data present many important and remarkable facts. 

 First of all, they show most emphatically that the a priori prediction 

 regarding the thermal movement of moisture as deduced from the laws 

 of surface tension and viscosity in their relation to temperature is not 

 strictly realized. According to these laws, the amount of water moved 

 from a warm to a cold column of soil should be the same for all moisture 

 contents, provided the soil mass exerts no influence upon water; inas- 

 much, however, as the soil does exert an adhesive force upon water, 

 the thermal translocation of moisture should increase with a rise in 

 water content. Instead, the percentage of water moved from a warm 

 to a cold column of soil at both temperature amplitudes increases regu- 

 larly and rapidly ^-ith an increase in moisture content in all the different 

 types of soil until a certain moisture content is reached, and then it 

 begins to decrease with a further rise in the percentage of water. The 

 results then plot into a parabola, ^vith a maximum point instead of a 

 straight line. This maximum point of water thermal translocation is 

 significant in at least two ways: (i) It is quantitatively about the same 

 for all classes of soil and qualitatively the same for both amplitudes 

 of temperature; and (2) it is attained at entirely different moisture 

 contents in the various soils and at a comparatively low percentage 



