as been destroyed. This is an error, as the water
enters the drain at the joints, and not through the walls of the tile.
Underdrainage should be permanent in its character, and it is essential
that every piece of tile be sound and well-burned.

Vitrified clay tile is good for drainage, but no better than common
clay hard-burned.

Round or octagonal tile is the most desirable because it can be turned
in laying to secure the best joints. Collars are not needed in ordinary
drainage.

Cement tile is coming into general use in regions having no good clay.
Its durability has not been tested, but there is no apparent reason
that it should not be a good substitute for clay.

The Grade.--The outlet may fix the grade. If it does not, the main,
branches, and laterals should have a fall of 3 inches, or more, to the
100 feet. This grade insures against deposits of silt and gives good
capacity to the drains. If the outlet demands less fall in the system,
the main may be laid on a grade of only a half inch to the 100 feet
with satisfactory results. Such a small fall should be accepted only
when a lower outlet cannot be secured, and great care should be used in
grading the trench and laying the tile.

Establishing a Grade.--If the grades are light, they should be
established by use of a telescope level. Most of the cheap levels are a
delusion. A stake driven flush with the surface of the ground at the
outlet becomes the starting point, and by its side should be driven a
witness stake. Every 100 feet along the line of the proposed drain and
laterals similar stakes should be driven. Their levels should then be
taken, and when the fall from the head of the system to the outlet is
known, the required cut at each 100-feet station is easily determined.
It may be necessary to reduce or increase the grade at some point to
get proper depth in a depression or to save cutting when passing
through a ridge.

Cutting the Trenches.--There are ditching-machines that do efficient
work. The best are costly. Most of the work on farms will continue to
be done with ditching-spades. The ground should be moved when wet, so
that labor can be saved.

A line should be used to secure a straight side to the trench. The
grade should be obtained by means of a system of strings. If two light
poles be pushed into the ground at each 100-feet station, one on either
side of the proposed trench, and a string be drawn across at a point
5-1/2 feet above the bottom