n interior
diameter. Sections of the 2-1/4 inch make collars for the 1-1/4 inch, and
sections of the 3-1/2 inch make collars for the 2-1/4 inch. The 3-1/2 inch
size does not need collars, as it is easily secured in place, and is only
used where the flow of water would be sufficient to wash out the slight
quantity of foreign matters that might enter at the joints.

[Illustration: Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID.]

Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID.

*The size of tile* to be used is a question of consequence. In England,
1-inch pipes are frequently used, but 1-1/4 inch(10) are recommended for
the smallest drains. Beyond this limit, the proper size to select is, _the
smallest that can convey the water which will ordinarily reach it after a
heavy rain_. The smaller the pipe, the more concentrated the flow, and,
consequently, the more thoroughly obstructions will be removed, and the
occasional flushing of the pipe, when it is taxed, for a few hours, to its
utmost capacity, will insure a thorough cleansing. No inconvenience can
result from the fact that, on rare occasions, the drain is unable, for a
short time, to discharge all the water that reaches it, and if collars are
used, or if the clay be well packed about the pipes, there need be no fear
of the tile being displaced by the pressure. An idea of the drying
capacity of a 1-1/4-inch tile may be gained from observing its _wetting_
capacity, by connecting a pipe of this size with a sufficient body of
water, at its surface, and discharging, over a level dry field, all the
water which it will carry. A 1-1/4-inch pipe will remove all the water
which would fall on an acre of land in a very heavy rain, in 24
hours,--much less time than the water would occupy in getting to the tile,
in any soil which required draining; and tiles of this size are ample for
the draining of two acres. In like manner, 2-1/2-inch tile will suffice
for eight, and 3-1/2-inch tile for twenty acres. The foregoing estimates
are, of course, made on the supposition that only the water which falls on
the land, (storm water,) is to be removed. For main drains, when greater
capacity is required, two tiles may be laid, (side by side,) or in such
cases the larger sizes of sole tiles may be used, being somewhat cheaper.
Where the drains are laid 40 feet apart, about 1,000 tiles per acre will
be required, and, in estimating the quantity of tiles of the dif