Uiider-Diainage. 
577 
mcnts, of wbicli details were publislied in the Journal of your Society, 
vol. XX., part 2. Numerous subseqiient experiments corroborate 
those details. By referring to the Hinkworth experiments, it wiU be 
seen that, on the occasion of a fall of rain of half-an-inch (January 
10, 1857), the flow of water from the under-drains was increased from 
910 gallons per acre (which was the flow on the 9th) to 2420 gallons ; 
•while in the clay lands, which had been considered to be impermeable, 
the discharge was increased from 125 gallons per acre to 5150 gallons 
on the same dates. This difierence is to be accounted for by the fact 
that the distance between the occasional drains in the free soil had 
been increased, by the guide of test-holes, to 58 yards, while the 
distance between the parallel drains of the clay soils was only 8i 
yards. In each case, the land had been equally wet, and was 
equally well-di-ained. To realise the efiect of close parallel drainage 
of the clay lands on the arterial channels of the country, we must 
remember that the extent of clay lands not drained, and yet to be 
drained, is 9,000,000 of acres. These 9,000,000 of acres are dis- 
persed all over the countiy ; and the quantity of land that might be 
placed under water, by default of outfall (say 10 inches deep), were 
the full extent drained, would be upwards of 200,000 acres. Before 
draining, it is possible that the same quantity of water might have 
found its way over the saturated surface, and have bem lodged in the 
hollows and ditches for gradual passage to the outfalls ; now it is no 
sooner discharged than it is delivered by improved tributary water- 
courses into the main valleys to collect there for want of sufficient 
outfall to the sea. 
The free soils form a proportion of more than half of the lands 
stlU requiring drainage ; they are estimated at 12,000,000 of acres. 
They consist of a very large proportion of the wet land of the West 
of England, of Wales, and of the North of England and Scotland. 
The Devonian, the Silurian, and Cumbrian districts are of this cha- 
racter, and the saturated beds of the old red sandstone, the new red 
sandstone, the Bagshot sand, and the various drift superficial deposits, 
may also be so classified. If critically examined it will be found 
that the wet soils of these formations consist either of the debris from 
higher land, sat\rrated with the water of pressirre sinking from the 
heights into the lower valleys, or from the water having travelled 
through a wide region of a free stratum to the surface where that 
stratum outcrops. To appreciate the advantage of draining the free 
soils by the fewest number of drains (indicated by test holes), that 
will set the water in motion, and lower the water level beyond the 
reach of active evaporation, we should have regard to the important 
fact that they suffer by reason of their formation and position from an 
excess of water beyond that which falls in the shape of rain upon 
them, and they are therefore immense stores from which we should 
draw with care and economy. It seems unnecessary to say that 
"whatever passes through the drains into the rivers cannot escape into 
the air by evaporation ; and that whatever the amount of water may 
be so arrested from the atmosphere, is a gain to the rivers in one 
shape or another. But it does not follow that this discharge augments 
2 P 2 
