RE.

From what has been stated in the preceeding chapter, it will be
sufficiently evident, that a supply of water is required as a component of
the soil, in which all plants are grown, in order to enable them to draw
from it, other components, which form their food; and that, as it is
necessary for them continually to take up a portion of this food, so is it
necessary, that moisture should be continually present, in order to render
it available by them.

Among other conditions to which the operation of applying water to the
soil should be subjected, there are some which are specially important: it
should never be either applied in _excess_, or unduly withheld; nor should
it ever be applied when of a temperature below that of the atmosphere in
which the plants to whose roots it is applied, are growing at the time of
its application.

There is a liability of applying water in excess, when the particular
stage of growth, the peculiar state of the weather, or the season of the
year, are not duly regarded: thus, an adult plant will consume more water
than an infant plant; and any plant, will decompose a larger quantity of
water, in sunny weather, when evaporation is going on briskly, than in
cloudy weather, when it is scarcely perceptible; again, in the summer
season, a much larger quantity will be appropriated, than in the winter.
Water has been applied in excess, whenever the soil becomes soddened or
saturated therewith; but great as this evil is, it is equalled in its
injurious effects, by falling into the opposite extreme, and withholding a
quantity sufficient to render the constituents of the soil, available as
food to the roots of plants placed in it.

The necessity of applying water, of a temperature equal to that of the
soil, is rendered evident by a reference to the natural conditions by
which the soil is watered. In a small and nearly globular form, the water
gathered up by the action of the sun, and forming the clouds above us, is
precipitated through the atmosphere, and there its temperature becomes
equalized or assimilated with that of the medium through which it has been
passing; and although in our own latitude, we perhaps fail to discover any
material degree of warmth in the drops of rain as they fall, yet in
eastern climes, we cannot but imagine, that after having been submitted in
the thin strata of the clouds to the action of the sun, they must
previously to entering the soil, have imbibed some portio