68 
THE TEMPEEATURE OF PLANTS, AND OF THE GROUND. 
The cultivation is the same as for the other stove species, viz., during the season of 
growth and flowering, a good supply of water to the roots, a humid atmosphere, a free 
circulation of pure air, and a well-drained soil, composed of light loam, heath-mould and 
sand, are its requisites. It may be increased by cuttings of the half-ripened wood, planted 
in pots of the same soil, and placed in a gentle bottom heat. 
TPIE TEMPERATURE OF PLANTS, AND OF THE GROUND. 
(Continued from Page 39.) 
By John Towers, Esq. 
We left the subject by an endeavour to prove that heat, applied at the bottom of any 
vessel, quickly raises the temperature of a volume of water contained therein. Now, to apply 
this very important truth to the advantage of practical horticulture, we should bear in mind 
that the ground, at the depth of a very few feet, is warmer during cold weather than it is at 
the surface, and, therefore, that the natural heat must ascend, and be carried off with the 
vapour, which — if the subsoil be charged with water — must be formed at its expense. 
Parkes, in proof, assumes the following position : — " Water," he says, " is a powerful 
radiator of heat, i. e., it cools quickly. The phenomena of the production of cold by 
radiation and evaporation are exemplified by exposing water warm enough to give off 
visible vapour in one saucer, and an equal bulk of water drawn from a well. The former, 
in a sharp frosty morning, will exhibit ice the sooner ; and, again, boiling water thrown on 
the ground, will freeze more quickly than cold water. The powers of evaporation and 
radiation combined — and of radiation chiefly — are represented in this experiment by 
the order of congelation of the two vessels, in point of time ; but the difference of heat 
emitted by each is immense, as appears from reference to the constituent heat of vapour." 
Again: — "As the temperature of water in land diminishes according to the varying 
conditions of the atmosphere, by radiating its heat into the air above its specific gravity 
increases ; and the superficial stratum, which is the first cooled, descends by its augmented 
density, and is replaced by the warmer and specifically lighter portions from below, which 
become cool in turn, and successively sink. Thus water, though it does not conduct heat 
downwards, becomes, when superficially warmed, a ready vehicle of cold in that direction. 
As, then, excess of water produces cold, those soils only can be exempt from this chilling 
influence which are not naturally retentive of water, or are secured by having been deeply 
and adequately drained." 
I shall close my trespasses upon Mr. Parkes's able Essay by the following abbreviated 
extract upon the depth and uniform action of drains. 
" If drains are not deeper than the worked bed, either of field or garden, water will 
remain in a stagnant state, and, consequently, must chill the roots of plants, and reduce 
the temperature of the superposed mass of cultivated ground. Gardeners and florists are 
aware of the injurious influence of water when supplied constantly in a pan instead of upon 
the surface of the soil, and bottom ivater, as it is sometimes aptly called, produces the same 
evil consequences, when it stagnates too near the surface of the great agricultural bed. 
" Superficial drainage is comparatively of little value, and is, perhaps, exemplified in 
its worst practical form by land tortured on the ridge and furrow system " (on the notion, 
as expressed in a note, "that on an undulating surface more stuff would grow than on 
a plane one "). 
Open drains are objected to, on the ground that " much of the rain precipitated on 
the surface necessarily passes into them before it has permeated the whole mass." 
I remark here, that wherever the rounded ridge and deep furrow are employed, the 
latter becomes full of water, as the clay lands were seen to be to a frightful extent in 
February, March, and April of 1848 ; and when so, we may be satisfied that drainage is 
either absent, or in a very defective, inefficient condition. 
