THE CULTIVATOR. 
11 
lure, water percolates through them freely. These, accordingly, 
form the natural conduits or channels for the water which is below 
the surface, when finding its way from a higher to a lower level. . 
When any bed or stratum of this kind, in which water is perco 
lating, crops out to the surface, the water which it contains will flow 
out and form a burst or spring, oozing over and saturating the 
ground, as in the foregoing figure 1, which represents a section of 
the ground, from C to D. 
When water is, in like manner, percolating through one of these 
pervious strata, and meets any obstruction, as a rock or bed of clay 
at A, Fig. 2, it is stopped in its progress and, by the pressure of 
the water from a higher source, it is forced upwards, and thus 
saturates the superjacent soil, as from D to E, forming springs, or a 
general oozing. 
In either of tiiese cases, and they are the most frequent that oc¬ 
cur in practice, the object of the drainer is to reach the water in 
its subterraneous channel before it shall arrive at the surface, and 
to carry it away in a drain. 
By cutting a drain at A, Fig. 1, the water of the stratum of 
sand CE, is cut off before it reaches the surface at C, where it 
forms the swamp CD. 
In like manner, in Fig. 2, by forming a drain at C or F, the 
water is cut off in its channel AB, and thus, in relieving the pres¬ 
sure from the higher source, by giving egress to the water through 
the drain, the cause of the wetness from F to D is removed. 
In looking at the sloping surface of any tract of ground, as a 
field, in which there is an oozing or bursting out of water, we shall 
generally distinguish the line where the wetness begins to appear on 
the surface, extending over a considerable space, x x x x x, Fig. 3, 
£ $ | / v 
the effects appearing in the wetness of the ground farther down the 
slope, as y y y- The line where the wetness begins, and which is 
generally rendered perceptible by the change of color of the soil, 
the tendency to produce subaquatic plants, and other indications of 
wetness, marks for the most part nearly the course which the line 
of the drain should follow. By cutting a drain nearly in this line, 
as from G to A, and from L to A, sufficiently deep to reach the 
porous stratum in which the water percolates, we shall intercept 
it before it reaches the surface, and by carrying it away in some 
convenient outlet, AB, remove the cause of wetness. 
This accordingly forms, in the greater number of cases, the rule 
adopted in practice for the laying out of drains upon the surface, 
the line is drawn nearly at or a little above, the line of wetness, or, 
to use the common expression, between the wet and the dry. 
Should the line of drain be drawn too much below the line of 
wetness, as at G, Fig. 1, then the trench would fail to intercept 
the water; and further, if it were filled with earth, stones and other 
substances, in the way to be afterwards described, the whole, or a 
part, of the water would pass over it, and the injury be unremoved. 
Again, should the line be too much above the line of wetness, as 
at H, the drain would fail to reach the channel of the water, and so 
would be useless. 
It is for this reason that, in common practice, the rule is, to draw 
the line of the drain nearly between the wet and the dry, or a little 
above it, taking care to give it the necessary descent, and to form 
it of sufficient depth to reach the pervious bed or stratum in which 
the water is contained. 
But as water may arrive at the surface in different ways, and the 
wetness be produced, by different causes, so variations from this 
rule of lining out the drain may be required, and the judgment of 
the drainer is to be shown in adapting the course of his drain to 
the change of circumstances. 
Sometimes, in a hollow piece of ground, feeders may reach the 
descent, as in Fig. 4; and the water may be forced upwards by 
the pressure from each side of the hollow, and thus form the swamp 
from A to B. It may not be necessary here to cut a trench on each 
side along the line of wetness at A and B; a single trench C, cut in 
the hollow, and giving egress to the water, may relieve the pres¬ 
sure and remove the swamp. 
Sometimes upon a sloping surface, one pervious stratum, in 
which water percolates, may produce more than one line of springs, 
as B and A, in figure 5. Here a single drain cut at B will remove 
the cause of wetness at both swamps, without the necessity of the 
drain at A. 
And, in practice, it is well to wait to mark the effect of a drain 
cut in the higher part of the slope to be drained, for these effects 
often extend further than might be anticipated, removing springs, 
bursts, or oozings, at a great distance. 
!iij §m 
On the other hand, a single swamp, as from B to A, in the fig. 
6, may be produced, and yet one drain at B may be insufficient to 
remove it. In this case, the water being brought to the surface!) 
more than one channel, it is necessary to form several drains to reach 
the several beds in which the water is contained, as at B, C, and D. 
