grade of the outlet (3.50) or a height of 3
inches from the brook level. On the floor thus made, there should be laid
the tiles which are to constitute the outlets of the several drains;
_i.e._, one 3-1/2-inch tile for the line from the silt-basin, two
1-1/4-inch for the lines _F_ and _G_, and one 2-1/4-inch for the main line
_E_. These tiles should lie close to each other and be firmly cemented
together, so that no water can pass outside of them, and a rubble-work of
stone may with advantage be carried up a foot above them. Stone work,
which may be rough and uncemented, but should always be solid, may then be
built up at the sides, and covered with a secure coping of stone. A floor
and sloping sides of stone work, jointed with the previously described
work, and well cemented, or laid in strong clay or mortar, may, with
benefit, be carried a few feet beyond the outlet. This will effectually
prevent the undermining of the structure. After the entire drainage of the
field is finished, the earth above these sloping sides, and that back of
the coping, should be neatly sloped, and protected by sods. An iron
grating, fine enough to prevent the entrance of vermin, placed in front of
the tile, at a little distance from them,--and secured by a flat stone set
on edge and hollowed out, so as merely to allow the water to flow freely
from the drains,--the stone being cemented in its place so as to allow no
water to pass under it,--will give a substantial and permanent finish to
the structure.

An outlet finished in this way, at an extra cost of a few dollars, will be
most satisfactory, as a lasting means of securing the weakest and most
important part of the system of drains. When no precaution of this sort is
taken, the water frequently forces a passage under the tile for some
distance up the drains, undermining and displacing them, and so softening
the bottom that it will be difficult, in making repairs, to secure a solid
foundation for the work. Usually, repairs of this sort, aside from the
annoyance attending them, will cost more than the amount required to make
the permanent outlet described above. As well constructed outlets are
necessarily rather expensive, as much of the land as possible should be
drained to each one that it is necessary to make, by laying main lines
which will collect all of the water which can be brought to it.

*The Main Silt-Basin.*--The silt-basin, at which the drains are collected,
may best be built b