DRAINAGE OF SOILS. 
323 
There are other soils of a similar nature, the drainage of which is 
easier accomplished, on account of their alternate beds of clay and 
fine sand lying much more regular. Under the alternate beds of 
clay and fine sand, which are often almost parallel to one another, is 
generally found an impervious body of clay, which keeps the veins 
of sand full of water, moistening the adjacent clay and running over 
it. As the main body of clay is seldom more than four or five feet 
below the surface, a drain must be cut to that depth through the 
middle of the field, if it has a descent from both sides; and if the 
ground declines all to one side, two drains will be required, the one 
near the upper side, to cutoff the water coming from the ground above, 
and the other near the lower extremity or lowest part, where the 
water in the different beds of sand will easily discharge itself. This, 
no doubt, will answer the purpose effectually—as the drains cross the 
different beds that contain the water, they will draw it from each, 
unless the field is of considerable extent, or have more hollows than 
one, in which case a drain must be made through every hollow. In 
draining land of this kind, there is seldom any need for using the 
auger, as the necessary depth of the drains reaches the impervious 
body of clay, the thickness of which being so great, that any water 
that is confined below will do no injury to the crop. 
Another description of land to which nearly the same treatment 
may be applied, is when the soil and sub-soil, to the depth of three 
four feet, is entirely porous, having under that a strong body of 
retentive clay; the rain water falling on the surface subsides till it 
meets with the clay, and then being obstructed from farther descent, 
the whole mass of porous soil above is filled with stagnant water, 
which not only retards the operations of agriculture, but also vege¬ 
tation. To remedy this, it requires only one or more drains, accord¬ 
ing to the situation of the field; and these require to be made no 
deeper than to reach a few inches into the clay, between which and 
the porous soil the greatest part of the water remains stagnant, 
although it does hot appear on the surface. If the land has a small 
descent from both sides, a drain cut through the porous soil into the 
.clav in the hollow will effectually draw off the water; but if the surface 
is undulating, as is often the case, it is necessary to make a drain 
winding through all the lowest places, and when it is almost level, or 
inclining to one side, the drains must be made across the slope, to 
some convenient outlet in the side of the field, taking care, in run¬ 
ning them, to give as much fall as that the water will run without 
standing still in their bottom. A particular account of the general 
dimensions and method of making drains adapted to such soils, will 
Y 3 
