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 porus stratum in which the water percolates, we shall intercept it before it reaches the surface, and by carrying it away in some convenient outlet, A B, 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 farther, if it were filled with earth, stones, and other substances, in the way to be afterward 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 circumstance.

Sometimes, in a hollow piece of ground, feeders may reach the descent, as in Fig. 4; and the water may be forced upward 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 VOL. 1.-Y

and B; a single trench C, cut in the hollow,

and

giving egress to the water, may relieve the pressure 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 Fig. 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 farther than might be anticipated, removing springs, bursts, or oozings at a great distance.

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 by 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.

These examples will show that one rule, with respect to the laying out of drains, is not applicable to all cases, but that the drainer should adapt his remedy as much as possible to the cause of injury. One object, however, to be aimed at in all cases of under-draining, is to reach the bed, channel, or reservoir in which the water is contained.

Before beginning to drain a field or tract of ground, it is frequently well to ascertain, by examination, the nature of the substances to be dug through.

At the upper part where the wet tract to be drained appears, or between the wet and the dry, let a few pits be dug. The place of each pit is to be marked out nearly in the direction of the proposed line of drain, six feet long by three in width, in which space one man, and, if required, two, can work. Let the earth be thrown out to the lower side, and to such a distance from the edge of the pit as not to press upon and break down the sides. Let these pits be cast out to the depth of five or six feet, or more, if necessary, so that we may reach, if

possible, the porous bed in which the water is contained. Should we find no water, then let us apply to the boring-rod, in order to ascertain at what depth the porous substance lies in which the water is contained.

Sometimes water will not be found until we come to a great depth. It may be so deep that we cannot reach it by any drain, or even by boring with the auger. In this case we are saved the labour of making the drain unnecessarily deep. Sometimes we shall proceed to a considerable depth without finding any appearance of water, when all at once, by breaking through some thin stratum, we shall reach it. The water is frequently seen, in this case, to boil up like a fountain, and this affords the assurance that we shall succeed in our object.

This species of preparatory examination by means of pits is, therefore, in many cases useful. It af fords the means of judging of the proper depth and dimensions of which the drain shall be formed; it prevents the committing of errors in the laying out of the lines of drains; and it enables the drainer to enter into contracts with his workmen with precision.

When we have thus, by sinking pits in various parts of our intended lines, obtained an idea of the nature of the ground, of the substances to be dug through, and of the depth of the water, we mark our lines of drains upon the ground.

This may be done by pins, or by a plough drawing a furrow along the intended line.

It is at this time very convenient to make a hand-sketch of the piece of ground to be drained, marking each line as it is laid off in the field, and noting the depth and direction in which the water is to run.

The lines being marked off in the manner described, these are to form the upper edges of the drains.