Draining for Profit, and Draining for Health | Page 4

seeds. The figures are thus explained by Dr.
Madden, from whose lecture they are taken:
"Soil, examined mechanically, is found to consist entirely of particles
of all shapes and sizes, from stones and pebbles down to the finest
powder; and, on account of their extreme irregularity of shape, they
cannot lie so close to one another as to prevent there being passages
between them, owing to which circumstance soil in the mass is always
more or less porous. If, however, we proceed to examine one of the
smallest particles of which soil is made up, we shall find that even this
is not always solid, but is much more frequently porous, like soil in the
mass. A considerable proportion of this finely-divided part of soil, the
impalpable matter, as it is generally called, is found, by the aid of the
microscope, to consist of broken down vegetable tissue, so that when a

small portion of the finest dust from a garden or field is placed under
the microscope, we have exhibited to us particles of every variety of
shape and structure, of which a certain part is evidently of vegetable
origin.
[Illustration: Fig. 1 - A DRY SOIL.]
Fig. 1 - A DRY SOIL.
"In these figures I have given a very rude representation of these
particles; and I must beg you particularly to remember that they are not
meant to represent by any means accurately what the microscope
exhibits, but are only designed to serve as a plan by which to illustrate
the mechanical properties of the soil. On referring to Fig. 1, we
perceive that there are two distinct classes of pores,--first, the large
ones, which exist between the particles of soil, and second, the very
minute ones, which occur in the particles themselves; and you will at
the same time notice that, whereas all the larger pores,--those between
the particles of soil,--communicate most freely with each other, so that
they form canals, the small pores, however freely they may
communicate with one another in the interior of the particle in which
they occur, have no direct connection with the pores of the surrounding
particles. Let us now, therefore, trace the effect of this arrangement. In
Fig. 1 we perceive that these canals and pores are all empty, the soil
being perfectly dry; and the canals communicating freely at the surface
with the surrounding atmosphere, the whole will of course be filled
with air. If in this condition a seed be placed in the soil, at a, you at
once perceive that it is freely supplied with air, but there is no moisture;
therefore, when soil is perfectly dry, a seed cannot grow.
[Illustration: Fig. 2 - A WET SOIL.]
Fig. 2 - A WET SOIL.
"Let us turn our attention now to Fig. 2. Here we perceive that both the
pores and canals are no longer represented white, but black, this color
being used to indicate water; in this instance, therefore, water has taken
the place of air, or, in other words, the soil is very wet. If we observe

our seed a now, we find it abundantly supplied with water, but no air.
Here again, therefore, germination cannot take place. It may be well to
state here that this can never occur exactly in nature, because, water
having the power of dissolving air to a certain extent, the seed a in Fig.
2 is, in fact, supplied with a certain amount of this necessary substance;
and, owing to this, germination does take place, although by no means
under such advantageous circumstances as it would were the soil in a
better condition.
[Illustration: Fig. 3 - A DRAINED SOIL.]
Fig. 3 - A DRAINED SOIL.
"We pass on now to Fig. 3. Here we find a different state of matters.
The canals are open and freely supplied with air, while the pores are
filled with water; and, consequently, you perceive that, while the seed a
has quite enough of air from the canals, it can never be without
moisture, as every particle of soil which touches it is well supplied with
this necessary ingredient. This, then, is the proper condition of soil for
germination, and in fact for every period of the plant's development;
and this condition occurs when the soil is moist, but not wet,--that is to
say, when it has the color and appearance of being well watered, but
when it is still capable of being crumbled to pieces by the hands,
without any of its particles adhering together in the familiar form of
mud."
As plants grow under the same conditions, as to soil, that are necessary
for the germination of seeds, the foregoing explanation of the relation
of water to the particles of the soil is perfectly applicable to the whole
period of vegetable growth.