Letter from Lord Palmerston. 
347 
keop to itself moisture enouj2^h to supply the wants of vegetable 
roots. The good effects then of draining upon the atmosphere 
of the district drained are demonstrable in theory, and anybody 
who, like me, has had drained a large extent of land, which 
before had been very wet, will have amply experienced those 
good effects in practice. The improvement in the atmosphere 
of that ])art of the valley of the Test, which extends from a mile 
above Romsey to two miles or more below it, is most striking 
and satisfactory, and is entirely owing to the drainage works 
which have been executed within those limits. 
But then as to the effect of under-draining upon the supply of 
water to rivers : rivers are supplied with water by rivulets 
which flow into them, and by water which rises from springs in 
their beds as they flow along. The rivulets will probably be 
increased in volume by drainage works, because they will be 
made the outfall for the drainage of land on higher elevations. 
Then as to the water which was before contained in the four or 
five upper feet of the land through which the river flows : that 
water, instead of being evaporated into the atmosphere, is carried 
along the under-drain and is delivered into the river at the 
earliest point at which the descending level of the river will give 
a sufficient outfall ; and supposing the depth of the drain to be five 
or six feet, in a river of average rapidity of current, the drained 
water may be discharged into the river at no very great distance 
from the beginning of the system of drains. Then as to the 
feeding springs which rise up in the bed of rivers, the only 
water that is withdrawn from them is that which would have been 
contained in the four or five feet of the upper surface of adjoining 
lands ; and I have already shown that, as regards such water, the 
river is a gainer, and not a loser, by the drainage. All the 
Avater in the soil below four or five feet from the upper surface of 
the land will, as before, find its way in springs to the bed of the 
river, without being in any way diverted from its course by the 
drainage of the upper surface. 
That this has been the case with the Test I can assert by 
experience, for the volume of its waters has not been in the 
slightest degree affected by the drainage works in adjoining lands. 
It has so happened that the river has been much fuller of water 
during the last two years than it had been for several years 
before, but that was owing to causes quite unconnected with the 
drainage works. 
My dear sir, yours faithfully, 
Palmerston. 
J. JB. Denton, Esq. 
VOL. xxir. 
