he soil, while
their beds are often compacted by the running water and the heat of the
sun, so that they become water-tight, and do not admit water from the
lower parts of the soil.

The sides of these drains are often covered with weeds, which spread
their seeds throughout the whole field. Open drains are not only a great
obstruction to the proper cultivation of the land, but they cause much
waste of room, as we can rarely plow nearer than within six or eight
feet of them.

There are none of these objections to the use of under-drains, as these
are completely covered, and do not at all interfere with the
cultivation of the surface.

[With what materials may under-drains be constructed?

Describe the tile.]

Under drains may be made with brush, stones, or tiles. Brush is a very
poor material, and its use is hardly to be recommended. Small stones are
better, and if these be placed in the bottoms of the trenches, to a
depth of eight or ten inches, and covered with sods turned upside down,
having the earth packed well down on to them, they make very good
drains.

TILE DRAINING.

The best under-drains are those made with tiles, or burnt clay pipes.
The first form of these used was that called the _horse-shoe tile_,
which was in two distinct pieces; this was superseded by a round pipe,
and we have now what is called the _sole tile_, which is much better
than either of the others.

[Illustration: Fig. 4--Sole Tile.]

[Why is the sole tile superior to those of previous
construction?

How are these tiles laid?

How may the trenches be dug?]

This tile is made (like the horse-shoe and pipe tile) of common brick
clay, and is burned the same as bricks. It is about one half or three
quarters of an inch thick, and is so porous that water passes directly
through it. It has a flat bottom on which to stand, and this enables it
to retain its position, while making the drain, better than would be
done by the round pipe. The orifice through which the water passes is
egg-shaped, having its smallest curve at the bottom. This shape is the
one most easily kept clear, as any particles of dirt which get into the
drain must fall immediately to the point where even the smallest stream
of water runs, and are thus removed. An orifice of about two inches is
sufficient for the smaller drains, while the main drains require larger
tiles.

These tiles are laid, so that their ends will touch each other, on the
bottoms of the trenche