mospheres, when we cannot supply them at
the same time with the same intensity of light, or provide for them the
same serene and unclouded sky. It should rather be our object to adapt
the plant to the climate of our country, since we cannot change the
climate to supply the natural circumstances, with which the plant is
favoured; and acting on this principle, we should never aim at supplying
the agents which would induce a premature and therefore debilitated
developement, when the whistling wind, and the drifting snow, tell us
that Nature, would have, at least the members of her vegetable kingdom,
be at rest.

Since however, it is apparent that during the depth of the winter season,
at least when wintry weather is present, the progress of plants in an
artificially heated atmosphere, ought not to be rapid, or unduly forced;
it by no means follows that no progression at all should be made: the
elements of growth maybe supplied; but the application of them should be
guided by moderation, being lessened at those particular periods when the
weather is least propitious, and increased during those periods when it is
most favourable. In the works of Nature we may ever learn a lesson of
consistency, for they are perfect: they teach us that food is requisite to
maintain the life of all those objects which are endowed with it; that
that food must undergo a process both of digestion and assimilation, ere
its purpose is fulfilled; and that each of these processes depend on the
action of natural agents. In the vegetable kingdom, heat and fight as
derived from a united source, are the agents appointed to bring about
these results, and in order to ensure their proper action, they must both
be present in a powerful degree: in artificial schemes of culture, we can
command a supply of the one, but the other is not within our power; our
consistency therefore depends on our applying so much of the one under our
controul, as will secure the united action of it, with the existing degree
of the other--consequently, _when light is absent, or deficient, heat
should also be diminished; and when light is present and abundant, heat
may safely be increased_.

CHAP. VIII.

ON THE ADMISSION OF AIR.

The question of the admission of air, is one of some importance. It is an
opinion, which was I believe first publicly brought forward by the late
Mr. Knight, that an influx of a large volume of the external atmosphere,
to the interior of forcing