ich it dries after
continued rain, thus enabling him to proceed at their proper season with
agricultural operations, which would otherwise have to be postponed for
a considerable time.

It would be out of place to enlarge here upon the mode in which draining
ought to be carried out; it may be remarked, however, that much
inconvenience and loss has occasionally been produced by too close
adherence to particular systems. No rules can be laid down as to the
depth or distance between the drains which can be universally
applicable, but the intelligent drainer will seek to modify his practice
according to the circumstances of the case. As a general rule, the
drains ought to be as deep as possible, but in numerous instances it may
be more advantageous to curtail their depth and increase their number.
If, for instance, a thick impervious pan resting on a clay were found at
the depth of three feet below the surface, it would serve no good
purpose to make the drains deeper; but if the pan were thin, and the
subjacent layer readily permeable by water, it might be advantageous to
go down to the depth of four feet, trusting to the possible action of
the air which would thus be admitted, gradually to disintegrate the pan,
and increase the depth of soil above it. It is a common opinion that if
we reach, at a moderate depth, a tenacious and little permeable clay, no
advantage is obtained by sinking the drains into it; but this is an
opinion which should be adopted with caution, both because no clay is
absolutely impermeable, even the most tenacious permitting to a certain
extent the passage of water, and because the clay may have been brought
down by water from the upper part of the soil, and may have stopped
there merely for want of some deeper escape for the water, and which
drains at a lower level might supply. In some cases it may even be
advisable to vary the depth of the drains in different parts of the same
field, and the judicious drainer may sometimes save a considerable sum
by a careful observation of the peculiarities of the different parts of
the ground to be drained.

_Subsoil and Deep Ploughing._--It frequently happens, when a soil is
drained, that the subsoil is so stiff as to permit the passage of water
imperfectly, and to prevent the tender roots of the plant from
penetrating it, and reaching the new supplies of nourishment which are
laid open to them. In such cases the benefits of subsoil ploughing and
deep ploughin