380 
THE COTTAGE GARDENER, 
March 18. 
I 
GENERAL PRINCIPLES OF FORCING. 
The pressure of enquiries for advice at this exceed- 
[ ingly busy period, renders it impossible to keep pace 
with every individual necessities, especially if treated 
singly and in detail. It will be well, therefore, occasion¬ 
ally to advert to, and explain, those general principles 
which are, as it were, the keys to the whole art of forcing, 
from the cherry up to the pine-apple; which two may he 
taken as the minimum and maximum extremes for the 
application of artificial warmth. 
First of all, heat. This we must consider under two 
heads—artificial and natural heat; for their effects are 
very different. Now that the sun gets much power, let 
a jealous eye be kept on all fires; more harm is done by 
an improper application of artificial heat than by star¬ 
vation, especially in the forenoon. Not every forcer is 
aware, or fully on his guard, as to the rapidly increasing 
rate at which temperatures rise on a bright morning in 
March or April, say from eight to ten o’clock, especially 
if a fire has been used through the night. Even as our 
politicians are wont to say, that election battles must be 
principally fought in the registration courts, so must 
the forcers chief battle be fought in that out-ofthe-way 
place, called a stoke-hole. Good gardeners, men of long 
experience, are much in the habit of taking a peep at 
l their fire-places; there is no leaving these things en¬ 
tirely to underlings, for it so happens that, not only is a 
crop of fruit perilled by injudicious firing, but the 
pocket also suffers. The safest practice is to cause every 
fire to be put out soon after six on every fine morning, 
the fire holes raked clean, and the fire immediately laid 
for lighting, which may be done about eleven o’clock. 
The remaining heat of the furnace walls will dry any 
rough material for lighting speedily. Of course, if the 
afternoon is likely to prove bright and warm, the fire 
will require but little encouragement; these things must 
be ruled by common sense and a prudent forecast. 
Every gardener is, or ought to be, weather wise, not pro¬ 
phetically for weeks or months, but, what is of far more 
importance, a capital forestaller of what the afternoon 
and night may be. 
And now as to sun-heat, the great elixir of the vege¬ 
table world. Let us in the first place remind our readers 
that it is much more economical than fire-heat, and not 
to despise it because it is cheap. 
Much sun-heat is thrown away, if we may apply such 
an expression, and this in the earlier part of the day is, 
we fear, unavoidable with those who are not real practi- 
cals. "W e here write guardedly, for better waste sun- 
heat than burn the foliage of plants, or, indeed, en¬ 
courage such an extreme temperature, as although it 
may not at once show what is technically termed burn¬ 
ing, or scorching, yet, by causing excessive vegetable 
perspiration, lays the foundation of weakness. Soon, 
however, after the sun has passed the meridian, let pre- 
parations be made by the forcer to turn his heat to 
account. It may be the day is fitfully blight—if so, a 
slight reduction of ventilation may be effected, and as 
eaily as two o clock, taking care to keep a jealous eye on 
the affair for another hour or so. A person in the habit 
i of watching the clouds can soon tell how to judge these 
I things. If they are in huge fields, of course there will 
be bursts of sunshine, with gluts of deep shade; if a 
| mottled sky, and the clouds in well-divided masses, 
much sun-heat may be indulged in; and so on with 
other classifications of the clouds. 
i But here another aspect of the question presents 
i itself we have yet another powerful agent to contend 
against the wind. In all cases of cutting winds, we 
; find it the best policy to sustain a moderate temperature; 
in fact, if very severe, to fall to the minimum point, or 
nearly so; by such means we are not driven to any 
material amount of ventilation, in the event of bursts 
of sunshine, which must be the case if much firing is 
used. In such cases, too, a considerable amount of 
atmospheric moisture may in general be applied, espe¬ 
cially whilst the houses are under ventilation ; this will 
soften the dryness of a too lively atmosphere, which 
carries with too great a rapidity dry heat from pipes or 
flues. 
Of course at night no air will be given under such 
circumstances; as before observed, the forcer should 
betake himself to as low a temperature as convenient. 
The hanging of canvass, or other breaks, before the 
apertures, is of excellent service under trying circum¬ 
stances, especially before points of entrance, which will 
generally be at the lower levels. 
As to the principles of ordinary ventilation, they are 
simple enough. What is termed “giving air,” by no 
means expresses all the purposes to which the opening 
of sashes may be employed. Air is given to let out sur¬ 
plus heat, to enliven and renew the contaminated or 
robbed atmosphere, and to dry up moisture in excess. 
Now, each of these processes require, it may be, a differ¬ 
ence either in the mode, or degree, or both. Thus, in 
order to let out surplus heat, the apertures at the highest 
level are mainly employed; for by a universal law, 
whether in-doors or out, heated ah will ascend. In 
order to enliven or renew the contaminated atmosphere, 
necessarily engendered through a partial exclusion of 
the refreshing current from without, there should be a 
specific supply from a low level, this supply delivered in 
a ratio nearly equal to the rate of the heated air passing 
out at the high level. If it does not amount to this, the 
exchange must take place at the high level, where it will 
be found, in all cases, a sort of rotary motion is going 
on, something like the phenomena presented by water 
in boiling, where, the fire being equal on all sides, the 
water springs like a fountain from the outsides, and 
descends with a beautiful equality down the centre. 
The giving air, in order to dry up moisture in excess, 
is simple enough. A lively current is necessary; a 
motion in the air, we mean, that can be felt. Under 
certain circumstances, however, a necessity arises for 
dispersing stagnated and hovering damps, with a guar¬ 
antee against cutting draughts, and this requires some 
caution. Let us put a case. Suppose a dull period in 
February, of “ fill dyke ” notoriety, the case in hand, 
some early forcing or plant-house, in which an indul¬ 
gence in atmospheric moisture, combined with a concur¬ 
rence of cloudy weather and a sluggish condition of air, 
have produced evident signs of stagnation ; and now let 
the problem be, How to disperse stagnation without 
lowering the temperature in any prejudicial degree ? We 
have a house, let us say, in which there is an entrance 
of air at a low level, and an outlet at a high level. Heat, 
artificial heat, most likely must be called in requisition, 
and if no danger exists from sun-warmth, which is not 
very imminent at this early period, the first point is to 
warm well the pipes or flues. Here, then, we have rare¬ 
faction, the basis of the whole affair—sunshine or not. 
And now comes the question of draught, or, as cur 
very cautious men say, “ cold currents.” Well, and cold 
currents, after several days coddling, are by no means 
congenial to vegetation, unused to excessive draughts 
through the medium of perspiration, accompanied with 
torpidity of system arising from a necessarily sluggish 
root-action in the early spring. It should here be 
observed, that the question of draughts or currents is 
one of demand and supply. If the demand, or in other 
words the escape of heated air, is faster than the entrance 
of the cold air, the current will be livelier, and vice 
versa. In a majority of cases, a copious admission of 
front air at so early a period would be incompatible 
with the well-being of highly-excited and tender plants; 
therefore the admissions at a low level, and conse¬ 
quently of cold air, must be well broken. But it is 
