CAPILLARY MOVEMENT OF SOIL MOISTURE. 9 



The plan of this experiment was to study the rate and extent of 

 movement of moisture from a wetted soil into an air-dry soil when 

 the two were brought in contact. The wetted soil was to contain 

 various percentages of moisture from near the point of capillary 

 saturation down to the wilting point. 



THE SOIL BOXES. 



The soil boxes or soil tubes for this work as first designed con- 

 sisted of galvanized iron boxes 6 by 6 inches in cross section and of 

 various lengths from 4 to 8 feet. 



It was soon found that the metal boxes, first used were not suffi- 

 ciently rigid. They were difficult to pack and the least jarring of the 

 box after it was packed and set in position was very apt to crack the 

 soil column. The second set of equipment, the boxes now in use, is 

 described later. 



ADDING THE WATER. 



Various methods were tried for adding the water to soil to be 

 wetted and at the same time insure a uniform pack offering no 

 mechanical obstacle in the movement of the moisture by capillarity. 

 The method finally adopted as giving the most uniform results for 

 the higher percentages of moisture was found not adapted to the 

 smaller percentages of moisture. In the first method, the water was 

 added to the soil after it had been packed and its distribution in that 

 part of the soil column left to capillary action. In the second method, 

 or the one used for the smaller percentages of moisture, the water 

 was added before packing. Where the water was to be added after 

 the soil was packed, a small furrow about 2 inches deep was made the 

 entire length of the part of the column to be wetted and the proper 

 amount of soil would take it up, and finally, with the last of the water 

 was added that part of the soil removed to make the furrow. The 

 wetted soil was then covered with plate glass and allowed to stand 

 24 hours before packing the air-dried part* of the column. As soon 

 as the dry soil was added the plate glass side was placed and sealed 

 in position and the box set in place and the experiment was under 

 way. 



When the moisture was added before packing, a mass of soil suffi- 

 cient for one pack was moistened to the desired percentage by adding 

 a weighted quantity of water. The mass was thoroughly mixed by 

 turning over and over several times on a piece of oil cloth. This 

 soil was then placed in the box in layers 2 inches in thickness and 

 tamped with a hard rubber tamping bar. The amount of tamping 

 was much a matter of judgment and testing, except that the same 



