s of the minors, at their junction with the mains,
will indicate their course--the minors curving always so as to more
nearly coincide, in course, with the current of water in the mains.

THE JUNCTION OF DRAINS.

Much difficulty arises in practice, as to connecting, in a secure and
satisfactory manner, the smaller with the larger drains. It has already
been suggested, that the streams should not meet at right angles, but
that a bend should be made in the smaller drain, a few feet before it
enters the main, so as to introduce the water of the small drain in the
direction of the current in the main. In another place, an instance is
given where it was found that a quantity of water was discharged with a
turn, or junction with a gentle curve, in 100 seconds, that required 140
seconds with a turn at right angles; and that while running direct, that
is, without any turn, it was discharged in 90 seconds. This is given as
a mere illustration of the principle, which is obvious enough. Different
experiments would vary with the velocity, quantity of water, and
smoothness of the pipe; but nothing is more certain, than that every
change of direction impedes velocity.

Thus we see that if we had but a single drain, the necessary turns
should be curved, to afford the least obstruction.

Where the drain enters into another current, there is yet a further
obstruction, by the meeting of the two streams. Two equal streams, of
similar velocity and size, thus meeting at right angles, would have a
tendency to move off diagonally, if not confined by the pipe; and,
confined as they are, must both be materially retarded in their flow. In
whatever manner united, there must be much obstruction, if the main is
nearly full, at the point of junction. The common mode of connecting
horse-shoe tile-drains is shown thus:

[Illustration: Fig. 50.--JUNCTION OF DRAINS.]

Having no tiles made for the purpose, we, at first, formed the union by
means of common hard bricks. Curving down the small drain toward the
direction of the main, we left a space between two tiles of the main, of
two or three inches, and brought down the last tile of the small drain
to this opening, placing under the whole a flat stone, slate, or bricks,
or a plank, to keep all firm at the bottom. Then we set bricks on edge
on all sides, and covered the space at the top with one or more, as
necessary, and secured carefully against sand and the like.

We have since procured branch