430 EXPERIMENT STATION RECORD. 



forms of apparatus devised by the author to determine the rate of 

 absorption, maximum aud minimum water-holding capacity, percola- 

 tion, and capillary rise of water in soils. One form of apparatus (with 

 which the results here reported were obtained) has already been 

 described in the Record (E. S. R., 7, p. 569). The improved apparatus 

 described consists of 2 soil tubes, with ground end held together by a 

 wide rubber band. Each of these tubes is of 2 sq. in. cross section and 

 holds exactly 100 cc. The lower tube is provided with a perforated 

 removable bottom. To prevent suction a small side tube enters the soil 

 tube just below the perforated bottom. The burette arrangement for 

 supplying and measuring the water is substantially as in the earlier 

 apparatus. 



The experiments reported were made with dark alluvial soil from 

 the Mississippi River bottoms, which contained 31.99 per cent of clay 

 and 43.7.3 per cent of fine silt. The soil was dried and pulverized 

 before use. 



The rate of .saturation was determined as follows: 



"Fifty grams of soil was plated in the soil tube and the burette raised so as to 

 bring the water in contact •with the soil. It was allowed to remain there for one 

 minute, then the burette was lowered for one minute and the amount absorbed read 

 off. This process was repeated each minute until the absorption became very slow, 

 when the water was allowed to stay in contact with the soil for a longer period. 

 Then the burette was lowered and left down until the reading was constant." 



In the first experiments the soil was used alone or mixed with 0.5 pec 

 cent of potash as muriate of potash or nitrate of potash. In all cases 

 the rate of absorption was rapid at first but gradually decreased as 

 saturation was approached. The stratum of capillary moisture rapidly 

 rose to the top of the soil and was slowly followed by one of saturation. 

 These movements, as well as the rate of absorption, were decidedly 

 decreased by the potash salts added. The time of complete saturation 

 was further noted on samples of soil to which had been added 0.5 per 

 cent K 2 as sulphate, chlorid, nitrate, phosphate (K :i P0 4 ), neutral and 

 acid carbonate, and hydroxid; 0.75 percent of CaO as caustic lime, 

 sulphate, nitrate, chlorid, phosphate (CaH 4 (P0 4 ) 2 4-Can PC).,) and car- 

 bonate; 0.5 per cent of MgO as caustic magnesia, sulphate, nitrate, 

 chlorid, and carbonate: and 0.1 and 0.5 per cent of Na 2 as acid car- 

 bonate, chlorid, and sulphate; 0.1 per cent of nitrogen as ammonium 

 sulphate, chlorid, and nitrate, and nitrate of soda; 0.001 per cent of 

 nitrogen as nitrate of soda; 1, 3, and 9 molecules of CaO + 1 molecule 

 of nitrate of soda, and 1 molecule of sodium sulphate+1 molecule of 

 calcium sulphate. 



Almost every salt had some effect on the rate of absorption. Most 

 of them decreased it, in some cases to an enormous extent. The lime 

 salts, however, with the exception of the phosphates and carbonates, 

 increased it to a slight extent. The alkaline salts of potash (with the 

 exception of carbonate), ammonium, and sodium in the order named 

 had the most marked effect in decreasing the rate of absorption. In 

 quantities usually applied in practice, however, this effect would be 



