156 Journal of Agricultural Research voi. v, N0.4 



attractive forces for water, as has been abundantly proved. Further- 

 more, if it is maintained that the attractive forces of the soil for water 

 are satisfied as soon as the soil is merely damped, then why should the 

 soil hold additional large amounts of water with such a great force that 

 it is impossible to extract it with mechanical means? It seems reason- 

 able, therefore, to believe that if the soil holds large amounts of water 

 with a great force, it should attract or absorb it with a force of equal 

 magnitude. 



MOVEMENT OF MOISTURE FROM A MOIST AND WARM COLUMN TO A 

 DRY AND COLD COLUMN OF SOIL WITH AN AIR SPACE BETWEEN 

 THE TWO COLUMNS 



In the precedmg section the thermal translocation of water was con- 

 sidered as occurring as water-film phenomena. There is still another 

 way in which this thermal movement of moisture might take place: 

 By vaporization and condensation of soil water from a point of high 

 temperature to a point of low temperature. It is well known that water 

 undergoes a transformation into the vapor state upon the application 

 of heat, and the quantity of liquid vaporized increases with a rise in 

 temperature. One of the remarkable characteristics of aqueous vapor 

 is its sensitiveness to heat, changing from a gaseous to a liquid state, 

 and vice versa, with very small variations in temperature. An excellent 

 paradigm of this latter fact is the relative humidity of the air at different 

 temperatures. 



Since the temperature gradient of the soil reverses itself during the 

 night — that is, it increases with depth — it is believed that there is a rising 

 of vapor or moist air from the warmer soil below to the colder soil above, 

 where the moisture is condensed. As a manifest proof of this theory, 

 the morning dew is cited. It is concluded, therefore, that a large part 

 of the water movement in soils is due to this process. 



There appear to exist no direct experimental data as to whether or 

 not there really is a translocation of moisture in soil at night, due to 

 upward movement of the moist warm air and the condensation of its 

 moisture at the cold soil above. Practically all of our present knowledge 

 upon the subject consists of theoretical deductions from practical observ^a- 

 tions. 



With the object of obtaining experimental evidence upon the subject 

 the following investigation was performed. Into brass tubes 8 inches 

 long and i K inches in diameter was placed moist soil at one end and dry 

 soil at the other and the two columns separated by an air space. This 

 air space was one-fourth of an inch in height and i % inches in diameter 

 and was produced by placing between the two columns of soil a ring of 

 cork, the two sides of which were closed with wire gauze that acted as 

 supports of the two soils and prevented their particles from coming in 

 contact. The tubes were then placed horizontally in the boxes shown 



