soles is a needless expense. On all these points, the book before us
gives confident opinions, with which we entirely coincide.

In regard to the depth of drains, it is shown, that in order that
they may _draw_, they should never be shallower than thirty inches,
and should always leave a depth of eighteen inches clear of the
draining materials, in order that the subsoil and trench plough may
have full freedom of action, without risk of injury to the drain;
while of the use of soles he says--

"I am a strenuous advocate for drainsoles _in all cases_; and even
when they may really prove of little use, I would rather use too many,
than too few precautions in draining; because, even in the most
favourable circumstances, we cannot tell what change may take place
beyond our view, in the interior of a drain, which we are never again
permitted, and which _we have no desire to see_."

This passage expresses the true principle of safety, by which, in
the outlay of large sums of money for improvements, the landowner,
and the holder of an improving lease, ought to be actuated. Though
great losses have already been incurred by shallow drains, and by
the rejection of soles, the practice, especially in the more
backward districts, still goes on, and thousands of pounds are still
expended upon the principles of a false economy, in repetition of
the same faulty practice. We know of drainings now going on to a
great extent, which will never permit the use of the subsoil plough;
and of the neglect of soles, upon soils generally of clay, but here
and there with patches of sand, into which the tiles must inevitably
sink. When a person drains his own land, of course reason is the
only constraint by which he can be withheld from doing as he likes