16 
the subsoil, which gradually acquires properties simi- 
lar to the upper soil, becomes dry and porous to a 
greater depth. Deeper ploughing, subsoiling, and 
trenching are now practicable; the plants have a lar- 
ger space through which to send their fibres in search 
of food; the elements of a fertile soil are brought 
into action; and the water in passing through the 
soil is made of great benefit, instead of doing such 
' injury by remaining stagnant. The result is, that after 
draining, the increase of produce is often enough to 
pay the cost of this operation in two or three years. 
It is obvious from these facts, that the deeper the 
drains, provided the water has a ready escape, the 
greater the depth of soil which is made available for 
vegetable nutrition. Experience has shown that 
water does find a ready escape into drains four feet 
deep, and that these are generally more beneficial 
than those laid nearer the surface. Both the depth 
and the distance apart must, however, be to a certain 
extent regulated by the circumstances of the case. 
There are no strong and good soils in which the 
water table naturally stands at a sufficient depth from 
the surface. All such soils will be materially benefit- 
ted by thorough draining, whatever their position 
may be, or the inclination of their surface. 
Thorough drainage prevents freezing out, or that 
process of crystallization of the surface which draws 
young plants from their beds. 
A given quantity of manure will last longer and 
do more service on drained than on undrained land. 
