-pipes to be made at the tile-works, such
as are in use in England, and find them much more satisfactory. The
branches may be made to join the mains at any angle, and it might be
advisable to make this part of both drains larger than the rest, to
allow room for the obstructed waters to unite peacefully.

[Illustration: Fig. 51. BRANCH PIPES.]

The mains should be from three to six inches deeper than the minors. The
fall from one to the other may usually be made most conveniently, by a
gradual descent of three or four feet to the point of junction; but with
branch-pipes, the fall may be nearly vertical, if desired, by turning
the branch upward, to meet the small pipe. It will be necessary, in
procuring branches for sole-tiles, to bear in mind that they are "rights
and lefts," and must be selected accordingly, as the branch comes in
upon the one or other side of the main.

The branch should enter the larger pipe not level with the bottom, but
as high as possible, to give an inch fall to the water passing out of
the branch into the main, to prevent possible obstruction at the
junction.

DRAINAGE INTO WELLS, OR SWALLOW HOLES.

In various parts of our country, there are lands lying too flat for
convenient drainage in the ordinary methods, or too remote from any good
outlet, or perhaps enclosed by lands of others who will not consent to
an outfall through their domain, where the drainage water may be
discharged into wells.

In the city of Washington, on Capitol Hill, it is a common practice to
drain cellars into what are termed "dry wells." The surface formation is
a close red clay, of a few feet thickness, and then comes a stratum of
coarse gravel; and the wells for water are sunk often as deep as sixty
feet, indicating that the water-table lies very low. The heavy storms
and showers fill the surface soil beyond saturation, and the water
gushes out, literally, into the cellars and other low places. A dry
well, sunk through the clay, conducts this water into the gravel bed,
and this carries it away. This idea is often applied to land drainage.
It is believed that there are immense tracts of fertile land at the
West, upon limestone, where the surface might readily be relieved of
surplus water, by conducting the mains into wells dug for the purpose.
In some places, there are openings called "sink-holes," caused by the
sinking of masses of earth, as in the neighborhood of the city of St.
Louis, which would afford outlet