Oji the Rain and Drainage - Waters at Eothamsted. 
329 
substances the small solvent action of rain results rather in their 
more equable distribution throughout a limited area of soil than 
in their removal from it. 
The behaviour of rain towards the diffusible salts contained 
in a soil may be illustrated by some percolation experiments 
recently carried out in the Rothamsted Laboratory. The perco- 
lator used consisted of a large glass bottle from which the 
bottom had been removed ; the bottle was fixed in an upright 
position, mouth downwards. A disk of copper gauze, covered 
by a disk of filter-paper, was laid inside the bottle at the 
lower end, and upon this 7 lbs. of a finely-powdered, air-dried, 
arable soil from one of the Rothamsted fields. The soil was 
well shaken in, so as to lie as compactly as possible. The 
column of soil thus obtained was about 8 inches in height, 
and 4^ inches in diameter. Pure water was then poured on 
the surface of the soil, while the neck of the percolator was 
connected with an air-pump (an ordinary Bunsen filter-pump 
was employed) to draw away the air contained in the dry- 
soil, and thus allow the water to descend without disturbing 
the coherence of the column. Without this precaution it was 
found that the air escaped upwards through the water, forming 
channels in the soil. In 2^ hours from the application of the 
water the whole column was saturated, and dropping com- 
menced. The drainage -water was collected in successive 
portions, and analysed with the following results : — 
Table XXVII. — The Amount and Composition of the Drainage- 
Water obtained in Successive Extracts from an Arable Soil. 
Water 
put on. 
Grams. 
Drainage- 
Water. 
Grams. 
Composition of Drainage- Water. 
Chlorine. 
Nitrogen as Nitric Acid. 
Per Million. 
Grams. 
Per Million. 
Grams. 
50 
10G8-5 
0-05343 
188-3 
0-00942 
1000 1 
50 
26G-0 
0-01330 
82-7 
0-00414 
50 
21-3 
0-00106 
8-0 
0-00040 
100 
100 
none 
none 
1-7 
0-00017 
1100 
250 
0-06779 
0-01413 
The effect of the rapid percolation of water through a dry 
soil, free from cracks and fissures, is certainly very remarkable. 
From the 7 lbs. of soil experimented on more than three-quarters 
of the diffusible salts are removed in the first 50 cubic centimetres 
2 A 2 
