efore any drains are brought to it, and the work may
proceed simultaneously with that at the outlet. It should be so placed
that its center will lie exactly under the stake which marks its position,
because it will constitute one of the leading landmarks for the survey of
the drains.(17)

Before removing the stake and grade stake, mark their position by four
stakes, set at a distance from it of 4 or 5 feet, in such positions that
two lines, drawn from those which are opposite to each other, will
intersect at the point indicated; and place near one of them a grade
stake, driven to the exact level of the one to be removed. This being
done, dig a well, 4 feet in diameter, to a depth of 2-1/2 feet below the
grade of the outlet drain, (in the example under consideration this would
be 5 feet below the grade stake.) If much water collects in the hole,
widen it, in the direction of the outlet drain, sufficiently to give room
for baling out the water. Now build, in this well, a structure 2 feet in
interior diameter, such as is shown in Fig. 24, having its bottom 2 feet,
in the clear, below the grade of the outlet, and carry its wall a little
higher than the general surface of the ground. At the proper height
insert, in the brick work, the necessary for tiles all incoming and
outgoing drains; in this case, a 3-1/2-inch tile for the outlet,
2-1/4-inch for the mains _A_ and _C_, and 1-1/4-inch for _B_ and _D_.

[Illustration: Fig. 24 - SILT-BASIN, BUILT TO THE SURFACE.]

Fig. 24 - SILT-BASIN, BUILT TO THE SURFACE.

This basin being finished and covered with a flat stone or other suitable
material, connect it with the outlet by an open ditch, unless the bottom
of the ditch, when laid open to the proper depth, be found to be of muck
or quicksand. In such case, it will be best to lay the tile at once, and
cover it in for the whole distance, as, on a soft bottom, it would be
difficult to lay it well when the full drainage of the field is flowing
through the ditch. The tiles should be laid with all care, on a perfectly
regulated fall,--using strips of board under them if the bottom is shaky or
soft,--as on this line depends the success of all the drains above it,
which might be rendered useless by a single badly laid tile at this point,
or by any other cause of obstruction to the flow.

While the work is progressing in the field above, there will be a great
deal of muddy water and some sticks, grass, and other