TEMPERATURE. 
seasons may be such as to be worthy of being 
considered equal to a difference of several degrees 
of latitude; hence the importance of selecting 
early or hardy kinds of grain, by which means 
the consequences of an unfavourable vegetating 
season may be much modified. The distribution 
of rain throughout the vegetating season con- 
stitutes also a very important feature of its cha- 
racter. Frequent rain, although not very copious, 
will be less favourable to vegetation than a 
greater quantity falling at longer intervals, pro- 
vided it is not so overpowering as to cause lodging 
of the crops. Other circumstances might be 
mentioned as worthy of notice; the number of 
clear and of cloudy days, and the state of the 
atmosphere in respect to the vapour contain- 
ed in it,—the lowness or highness of the dew 
point.” 
The maintaining of a preternatural tempera- 
ture by artificial means, ranging from those of 
mere special tropical shelter to those of the 
highest requisite fire or steam heat, constitutes 
the grand difference between the art of gardening 
and the art of farming, and comprises all the 
kinds and varieties of what is technically called 
forcing, and deals more or less with all exotic 
plants which will not perform the offices required 
from them, of growing, or flowering, or fruiting, 
in the open ground of the climate or situation in 
which they are cultivated. ‘Now in what may 
be termed the higher department of forcing, there 
are, perhaps, fewer objectionable points than in 
the lower scale—where the plants are not kept 
in pots, and are consequently liable to great dis- 
crepancy between their terrestrial and atmo- 
spheric temperatures. Much has been written 
on the latter; and in practice it has been found 
best to approximate it as nearly as possible to 
that climate in which the given species of exotic 
plants naturally acquires the highest perfection. 
Beyond this, nothing need or can be advanced ; 
but, with regard to what may be termed terres- 
trial temperature, something useful may be sta- 
ted. The vine, for instance, as regards tempera- 
ture, may be, and often is, so situated as to have 
its shoots in the climate of Syria, whilst at the 
same time its roots are in that of Britain. Such 
being the case, there need be less surprise at the 
ill success which occasionally accompanies its 
cultivation, than at the reputed inexplicable 
causes of bad setting, shriveling, and shanking 
of the grapes. The mean temperature of the 
soil, or that portion of the earth extending to 
several feet below its surface, is nearly the same 
as the mean temperature of the incumbent at- 
mosphere. The soil of ‘England, so far as the 
generality of roots penetrate, may therefore be 
estimated at about 50° Fahr. for the average. 
In Armenia and Syria (which may be reckoned 
the native region of the vine, for there, since the 
remotest accounts of history, it has felt itself at 
home,) the mean temperature of the soil will not 
be below 60°; and in the growing season its tem- 
perature will, doubtless, be above 70°, correspond- 
ing with the temperature of the atmosphere 
which is imitated in the vineries of Britain, but 
forming a great discrepancy with the temperature | 
of the soil of this country. But, although this 
will be allowed to be bad, still the worst of the 
evil remains to be noticed. The above is only a 
medium case of general occurrence; and, al- 
though some may not be so widely different as 
10° in the action of temperature on root and 
branch, yet there are, in all probability, a greater 
number of cases in which the difference is con- 
siderably increased, from various causes power- 
fully tending to lower the temperature of the 
border. In order to illustrate some of the causes 
which have this tendency, let us make an ex- 
periment wherein the agencies bear close analogy 
to what actually occurs. Leta box, water-tight, 
be nearly filled with loose mould or peat, or sand, 
or even the composition of a vine border; let this 
be tolerably dry, in order to increase its capacity 
for water cooled to the temperature of 50°; then 
saturated with snow water a little above the 
freezing point. This process, with the aid of a 
frosty night, will bring the contents of the box 
below 40°, and is supposed to take place in the 
winter or early part of spring. If the box be 3 
feet deep, the sun’s rays will not affect it far be- 
low the surface, since water is not easily heated 
from above; and, besides, the heat through the 
day will, at that season, be greatly counteracted 
by the cold at night. As the season advances, 
rain may be expected of a temperature above 
60°; and this, under some circumstances, would 
produce a very considerable effect. Unfortunate- 
ly, however, the box was made water-tight; and 
its contents, being completely saturated with 
nearly gelid water, cold, and heavy, and mechani- 
cally immovable by the descending warmer and 
lighter fluid, the latter must recede by the 
surface in quest of an unoccupied lower level, 
after producing only a slight effect on the surface 
of the contents of the box. The analogy between 
this and a badly drained outside vine border is 
so obvious that it need not be traced ; similarity 
might, indeed, be substituted for analogy. Nor 
is it necessary to point out the injurious conse- 
quences that must accrue to the forcing vine. 
He that is not sufficiently impressed with this, 
has only to imagine his feet to be plunged in the 
one temperature, and his body in the other,—the 
bare idea of such will make him shudder. Let 
us now, with the same box, and similar materials, 
endeavour to produce a different result; com- 
mencing by piercing the bottom, and making a 
complete drainage; and, further, keeping the 
contents as dry as possible, and neither exposing 
them to the sleety shower, nor placing them ex- 
terior to the front of the vinery, where it would 
receive an overshot of snow from the slippery 
roof; but letting the surface be snugly covered, 
or thatched from all such drenching, till genial 
showers of the temperature of 60° or more begin 
ei 
419 | 
