is entirely an erroneous
assumption. If soils were impervious, how could they get wet?

"I assert, and pledge my agricultural reputation for the fact,
that there are no earths or clays in this kingdom, be they ever so
tenacious, that will not readily receive, filter, and transmit
rain water to drains placed five or more feet deep.

"A neighbor of mine drained twenty inches deep in strong clay; the
ground cracked widely; the contraction destroyed the tiles, and
the rains washed the surface soils into the cracks and choked the
drains. He has since abandoned shallow draining.

"When I first began draining, I allowed myself to be overruled by
my obstinate man, Pearson, who insisted that, for top water, two
feet was a sufficient depth in a veiny soil. I allowed him to try
the experiment on two small fields; the result was, that nothing
prospered; and I am redraining those fields at _one-half_ the
cost, five and six feet deep, at intervals of 70 and 80 feet.

"I found iron-sand rocks, strong clay, silt, iron, etc., and an
enormous quantity of water, all _below_ the 2-foot drains. This
accounted at once for the sudden check the crops always met with
in May, when they wanted to send their roots down, but could not,
without going into stagnant water."

"There can be no doubt that it is the _depth_ of the drain which
regulates the escape of the surface water in a given time; regard
being had, as respects extreme distances, to the nature of the
soil, and a due capacity of the pipe. _The deeper the drain, even
in the strongest soils, the quicker the water escapes._ This is an
astounding but certain fact.

"That deep and distant drains, where a sufficient fall can be
obtained, are by far the most profitable, by affording to the
roots of the plants a greater range for food."

Of course, where the soil is underlaid by rock, less than four feet from
the surface; and where an outlet at that depth cannot be obtained, we
must, per force, drain less deeply, but where there exists no such
obstacle, drains should be laid at a _general_ depth of
four-feet,--general, not uniform, because the drain should have a uniform
inclination, which the surface of the land rarely has.

*The Distance between the Drains.*--Concerning this, there is less
unanimity of opinion among engineers, than prevails with regard to the
question