a; and carbon, which they derive from carbonic acid gas, on the
liberation of the oxygen, which is one of its constituents; neither of
these, can however be appropriated, when in a free state, but only when in
a state of combination, and forming either a gaseous or a fluid body. It
is probable that nitrogen might be supplied to plants, through the medium
of the atmosphere in an artificial manner, by placing within any
structure, a portion of some of the volatile salts of ammonia, which
latter being given off, would at once supply the demands of vegetation.
Carbon might be applied, by the use of charcoal; and it is worthy of
experiment how far the _combustion of charcoal_, in plant structures, by
accelerating the formation of carbonic acid gas, may have a beneficial
influence on vegetation. The use of charcoal as an ingredient in the soil,
though doubtless partly, and perhaps principally mechanical, is
nevertheless in all probability rendered advantageous in this very way;
the slowness of its decomposition must however render the quantity
applied, very homoeopathic in its nature.

A series of experiments with the view of ascertaining the practicability
of continually supplying to the atmosphere, those qualities which plants
abstract from it, and of determining the manner, and the degree in which
they should be applied, would be one of the most interesting and important
matters, to which the minds of Horticultural reformers could possibly be
directed; but it is most essential, to remember, at the same time, "that
these are powerful agents, requiring much skill in their adaptation," and
capable of effecting serious injury and disappointment, if
indiscriminately applied.

CHAP. IX.

ON THE GROWTH OF MELONS.

It is barely possible to suppose any use to which a structure which during
the winter season had been devoted to the growth of Cucumbers, could be so
legitimately appropriated in the summer, as that of the growth of the
finer Melons of Persia, Cashmere, and the East. The superiority of such as
these, in every point of view, over those kinds, which have been long in
cultivation, would be an ample recompense for the appropriation of such
valuable space to their use; whilst in no other structure could the
peculiarities of the treatment they require, be so fully complied with,
and be rendered so completely under control, as in that under
consideration.

There are some peculiarities in the treatment of these Mel