On the Rain and Drainage - Waters at Rothamsted. 21h 
takes place. Some of these channels consist of surface-cracks, 
which, becoming partly filled with sand and small stones, remain 
partially open after dry weather has ceased. The deeper 
channels .are, however, not of this character, but are produced 
by the roots of plants, or to a still greater extent by the burrowing 
of worms. The soil drain-gauges we are now concerned with 
have furnished illustrations of both these actions. During the 
digging of the trenches round the gauges, barley-roots were 
observed penetrating the soil to a depth of 50 or 60 inches. 
When such roots decay, a small open channel is left through 
which drainage can take place. The burrowing of worms in 
the soil of the drain-gauges has proved a source of trouble in the 
collection of pure drainage-waters. Worms have not unfrequently 
appeared on the collecting funnel of the 20-inch gauge, having 
come through the soil above ; and what appear to be worm- 
casts, dropped from the holes of the perforated iron plates, are 
of still more frequent occurrence. Worms have also appeared, 
though much more rarely, on the collecting funnels of the 40- 
and 60-inch gauges. The holes made by worms thus descend 
to a considerable depth, and if sufficiently numerous, must have 
an important influence on drainage. 
The drainage-water from a soil may thus be of two kinds : it 
may consist (1) of rain-water which has passed, with but little 
alteration in composition, down the open channels of the soil ; 
or (2) of the water discharged from the pores of a saturated 
soil. This latter water, the true drainage of the soil, will itself 
escape to a greater or less extent through the channels already 
mentioned. The respective proportions of direct and general 
drainage will vary much in different soils, and under different 
circumstances. In a light soil, of naturally free drainage, chan- 
nels can play but an insignificant part, the rain being at once 
absorbed by the main body of the soil, and freely discharged 
again from its pores when saturated. In heavy soils, on the 
other hand, both the absorption and the discharge of water can 
take place but slowly, and the part which natural channels play 
in freeing the soil of water is more considerable. In a heavy 
soil direct channel-drainage will in most cases precede general 
drainage, a portion of the water escaping by the open channels 
before the body of the soil has become saturated ; this will 
especially be the case if the rain fall rapidly, and water accumu- 
lates on the surface. When the soil is saturated, general drainage 
will become active. After rain has ceased, and the surface 
is free from standing water, the drainage which occurs will be 
entirely due to the general discharge from the saturated soil. 
The two kinds of drainage-water here mentioned differ much 
in composition, the direct channel-drainage containing a much 
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