e and security. It will simplify the question if, in
treating the _theory_ of lateral drains, it be assumed that our field is
of this uniform inclination, and admits of the use of long lines of
parallel drains. In fact, it is best in practice to approximate as nearly
as possible to this arrangement, because deviations from it, though always
necessary in broken land, are always more expensive, and present more
complicated engineering problems. If all the land to be drained had a
uniform fall, in a single direction, there would be but little need of
engineering skill, beyond that which is required to establish the depth,
fall, and distance apart, at which the drains should be laid. It is
chiefly when the land pitches in different directions, and with varying
inclination, that only a person skilled in the arrangement of drains, or
one who will give much consideration to the subject, can effect the
greatest economy by avoiding unnecessary complication, and secure the
greatest efficiency by adjusting the drains to the requirements of the
land.

Assuming the land to have an unbroken inclination, so as to require only
parallel drains, it becomes important to know how these parallel drains,
(corresponding to the _lateral drains_ of an irregular system,) should be
made.

The history of land draining is a history of the gradual progress of an
improvement, from the accomplishment of a single purpose, to the
accomplishment of several purposes, and most of the instruction which
modern agricultural writers have given concerning it, has shown too great
dependence upon the teachings of their predecessors, who considered well
the single object which they sought to attain, but who had no conception
that draining was to be so generally valuable as it has become. The
effort, (probably an unconscious one,) to make the theories of modern
thorough-draining conform to those advanced by the early practitioners,
seems to have diverted attention from some more recently developed
principles, which are of much importance. For example, about a hundred
years ago, Joseph Elkington, of Warwickshire, discovered that, where land
is made too wet by under-ground springs, a skillful tapping of
these,--drawing off their water through suitable conduits,--would greatly
relieve the land, and for many years the Elkington System of drainage,
being a great improvement on every thing theretofore practiced, naturally
occupied the attention of the agricultural world