330 On the Rain and Drainage - Waters at Rothamsted. 
(^about If fluid oz.) of drainage-water, and almost the whole 
amount of the diffusible salts is obtained in the first 150 cubic 
centimetres of drainage-water. The column of water passing 
through the soil thus evidently dissolved the chlorides and 
nitrates at its lower edge, and kept pushing this solution before 
it as a narrow layer, which was finally expelled in the first 
portions of the drainage-water. 
To obtain this expulsion of the diffusible salts in so small 
an amount of drainage-water it is essential that the soil should 
be dry, and that the percolation of the water should take place 
rapidly. The experiment just quoted was intentionally aided 
by the air-pump, and was completed in less than 4 hours. 
Another experiment will illustrate what may be expected to 
take place when these conditions are altered. 
A column of soil similar to that just described was first 
exhausted of its own chlorides by the passage of water through 
it ; 0'3843 gram of pure chloride of sodium (equal to 334 lbs. 
per acre) was then dissolved in a little water, and poured on the 
surface of the saturated soil ; after standing a week, percolation 
was commenced, 120 cubic centimetres of water being placed 
each day on the surface, and about the same amount of drainage- 
water removed below. For the percolation of this amount of 
water without the aid of the air-pump nearly 24 hours were 
required. The results were as follows : — 
Table XXVIII. — Results of Percolation after Chloride of Sodium 
had been applied to the Soil. 
Water 
Drainage 
Chlorine in Drainage-Water. 
put on. 
obtained. 
Per Million. 
Grams. 
Grams. 
Grains. 
120 
117-1 
none 
none 
120 
119-4 
none 
none 
120 
115-1 
none 
none 
120 
120-2 
43-8 
0-00527 
120 
115-3 
202-0 
0-02329 
120 
118-9 
476-0 
0 -05059 
120 
114-0 
021-0 
0-07079 
120 
123-4 
425-0 
0-05245 
120 
118-9 
158-0 
0-01879 
120 
120-0 
39-8 
0-00478 
120 
119-4 
7-G 
0-00091 
1320 
1301-7 
0-23287 
