ling on the surface, and obliged to
find its devious way through the mazes of cracks and particles till it
gains an outlet at the bottom of four feet of clay, it does seem a
discouraging journey for the poor little solitary thing; but there is a
more correct view of the matter, which somewhat relieves the difficulty.

All the water that will run out of the soil has departed; but the soil
holds a vast amount still, by attraction. The rain begins to fall; and
when the soil is saturated, a portion passes into the drain; but it is,
by no means, the water which last fell upon the surface, but that which
was next the drain before the rain fell. If you pour water into a tube
that is nearly full, the water which will first run from the other end
is manifestly not that which you pour in. So the ground is full of
little tubes, open at both ends, in which the water is held by
attraction. A drop upon the surface drives out a drop at the lower end,
into to the drain, and so the process goes on--the drains beginning to
run as soon as the rain commences, and ceasing to flow only when the
principle of attraction balances the power of gravitation.

PRESSURE OF WATER IN THE SOIL.

In connection with the passage of water through clay soil, it may be
appropriate to advert to the question sometimes mooted, whether in a
soil filled with water, at four feet depth, there is the same pressure
as there would be, at the same depth, in a river or pond. The pressure
of fluids on a given area, is, ordinarily, in proportion to their
vertical height; and the pressure of a column of water, four feet high,
would be sufficient to drive the lower particles into an opening like a
drain, with considerable force, and the upper part of such a column
would essentially aid the lower part in its downward passage. Does this
pressure exist? Mr. Gisborne speaks undoubtingly on this point, thus:

"We will assume the drain to be four feet deep, and the water-table
to be at one foot below the surface of the earth. Every particle of
water which lies at three feet below the water-table, has on it the
pressure of a column of water three feet high. This pressure will
drive the particle in any direction in which it finds no
resistance, with a rapidity varying inversely to the friction of
the medium through which the column acts. The bottom of our drains
will offer no resistance, and into it particles of water will be
pushed