INFLUENCE OF MOVEMENTS OF WATER 201 



It appears from these figures, that the soil, weighing about 

 3,175 grams, and containing probably about 5 per cent, of 

 moisture, was saturated by the addition of 850 grams of 

 water. The first 50 grams of water which passed through 

 after saturation contained rather more than three-fourths of 

 the chlorides and nitrates originally present in the soil, and 

 practically the whole of the soluble salts was removed in 

 the first 150 grams of drainage water 1 . The process of soil 

 extraction was completed in less than four hours. 



The illustration just given shows in a forcible manner how 

 salts are carried through the soil when a heavy rain falls on 

 previously dry earth, and the process of percolation is speedily 

 accomplished, so that diffusion is reduced to a minimum. In 

 the next experiment to be mentioned, the soil was saturated 

 with water before the experiment commenced, and percolation 

 took place very slowly ; opportunity was thus given for the 

 action of diffusion to be manifested. 



The object of the next experiment was to study the passage 

 through the soil, and the discharge into the drainage water, 

 of a dressing of saline manure applied at the surface. A 

 column of soil, quite similar to that used in the previous 

 experiment, had all its soluble salts removed by extraction 

 with water aided by the air-pump in the manner before 

 described. The mass of saturated soil was then disconnected 

 with the pump, and 0-3843 gram of chloride of sodium, dis- 

 solved in a little water, was distributed over the surface. The 

 chloride of sodium contained 0-23313 gram of chlorine ; it was 

 equivalent to a dressing of 3 cwts. of common salt per acre. 



1 This mode of extracting the soluble salts present in a soil is so simple 

 and effective that it has been largely adopted when determinations of the 

 nitrates or chlorides present in a soil are desired. Trans. Chem. Soc. 1882, 351. 



