150 
THE COTTAGE GARDENER. 
[December 5. 
iu the morning, if not left on all night, less trouble will 
be necessary, in ever and anon increasing its quantity— 
as a considerable rise from sun-heat in these circum¬ 
stances will be beneficial rather than injurious. The 
second advantage is, that less fuel will be required; a 
matter of considerable importance. Thanks to the im¬ 
proved modes of heating—some of the most ticklish of 
gardening operations are reserved for our amateur 
friends, who will have early cucumbers with the assist¬ 
ance of their dung-beds only. 
As low temperature at night is here a fruitful source 
of disaster, let us describe how it often happens. The 
plants are doing well, a sudden and severe frost comes; 
hurry-scurry, but not without method or forethought, fer¬ 
menting material is piled round the box or pit, and 
coverings are put over the glass in the most approved 
fashion; and the enemy is thus shut out, and safety 
reigns within. It is right, aye and good, for us to be 
aroused by the sight of an enemy; it is dangerous when 
that enemy retreats to repose upon the laurels of self- 
satisfaction and indolence. During the frost, the plants 
would be healthy and luxuriant; the temperature at 
noon, even with a sufficiency of air, would be 80° or up 
wards by sun-heat, and though most of the air was re¬ 
moved early, and coverings early put on, the plants would 
never grumble, though the temperatiu-e stood at 60° 
in the morning, though the grower might fret right 
loud about it. Rut now the frost goes as suddenly as 
it came; is the treatment changed likewise? Dull 
foggy warm weather succeeds the frost with its sunshine ; 
that of itself would have the tendency to render the 
jilants weak and watery. The temperature by day 
ranges from 65° to 70°. The linings used for the ex¬ 
clusion of cold are now rapidly fermenting and trans¬ 
mitting their heat. It has neither been deemed necessary 
to remove part of them again nor to pull them back from 
the sides of the pit or frame, or even much to lessen 
the amount of covering; nay, the good man congra¬ 
tulates himself, that if his temperature is not very high 
during the day, it is nearer 80° than 65° when he un- 
j covers in the morning; and in his mind’s eye he is 
already cutting twenty-inch cucumbers on Easter Sun- 
| day. But a season of clear weather again succeeds the 
; dull and foggy. What renders so buoyant the spirits 
j of the gardener must be equally grateful to the pets 
; over the dung-bed. Without thinking of the suddenness 
of the change, without dreaming of a shade, he clears 
the glass of every spot that would obstruct the light, 
and gives as much air as will prevent the temperature 
being unduly elevated, forgetting that in certain circum- 
! stances the effects of very hot and very cold air are al¬ 
most analogous. He returns to observe progress, and is 
astonished to find every leaf flagged ; the edges of many 
of them turned up and scorched, as if with a hot curling- 
iron, and their surface in many places as smooth and 
j shining as if a huge snail had left the marks of its trail. 
If by a close moist shady atmosphere, ho so far recovers 
1 1 is plants, it is so long before they escape from their de¬ 
bilitated state, and their watery condition renders them 
, such an agreeable repast for hosts of insects, that, as a 
question of profit and loss, it might require some in¬ 
genuity to decide between the cost of the tobacco for 
fumigating and the worth of the cucumbers. Had beat 
; been regulated by light, had the chief stimulus for ex¬ 
pansion been associated with the chief agent for the 
| assimilation of solid matter, fewer precautionary measures 
| would have been necessary, and failures less likely. 
Exactly similar results follow similar causes in our hot- 
| houses, greenhouses, and cold-pits, though the evils are 
| less quickly perceptible. Hence, I have uniformly re¬ 
commended the disuse of fermenting materials for placing 
round pits and frames for half-hardy plants in winter, 
j not merely on account of the damp thus fostered, but 
j because weak sickly growth would thus be encouraged- 
If necessity at times forces its adoption, it should either be 
removed when the occasion for its use has passed, or its 
presence counterbalanced by a plentiful supply of air 
during the night. “ Then what is the definite rule you 
would give us for the temperature of our plant-houses ? 
say some of our younger friends. No definite ride but j 
this: regulate the temperature within by the light, and 
temperature, and moisture, in the atmosphere without. 
As an example: here is a warm greenhouse; we say 
nothing of its ventilation in summer, because then it , 
can scarcely have too much,—our remarks apply chiefly to j 
late autumn, winter, and early spring. Its average tem¬ 
perature is 45° at night, and 50° during the day, with a , 
rise of five or ten degrees from sun-lieat, with plenty of 
air when the weather was mild without, especially in | 
autumn, but a more limited supply in spring, because j 
the air is then generally much drier and colder. But j 
supposing, that instead of an external temperature rang- i 
ing from 33° to 45°, we have ten, fifteen, or more degrees | 
of frost, shall we keep up the same temperature night 
aud day, and give air on similar principles. No; in- j 
stead of increasing the fire, we will, if at all convenient, 
cover the glass of at least a portion of the house, and 
thus so far retard the radiation of heat, and the con¬ 
densation of moisture in the atmosphere within ; and if 
that is not practicable, we will, rather than roast our 
plants, allow the temperature to fall five or eight degrees 
at night, and in this there will be a great advantage, for 
if the sun shines brisk the following day, it will take so 
much of its unaided heat to raise the houses incon¬ 
veniently high, that but a very limited portion of air 
will be necessary; and the less that can be done with 
the better; for cold air in frosty weather deprived of its 
moisture by congelation, is very scorching and destruc¬ 
tive in its effects. Rather than give much air in such 
circumstances where tender plants are concerned, we 
would prefer shading for a time. What holds true in the 
case of our warm greenhouses, is still more forcibly 
true in relation to other houses for plants and forcing, 
where the temperature is much higher. This will fur¬ 
ther appear, if we consider, 
Secondly. That the capacity of air for moisture in the 
shape of vapour is in a certain progressive ratio to its 
temperature, and that the rate of the condensation of 
that moisture upon the glass of the building is in pro¬ 
portion to the difference of the temperature within and 
that without. Thus the capacity of air for moisture at 
44° is doubled at 66°, and quadrupled at 99°. Take 
this in connection with the fact, that each square foot of 
glass will cool cubic foot of air per minute as many 
degrees as the difference existing between the internal 
and the external temperature, and that the moisture 
contained in that heated air will be deposited on the | 
glass as dew, and either through the laps find its way , 
out of the house, or fall over -the plants inside in tlie 
shape of drip; while the cooled air falls until it reaches 
the ground, and is then drawn towards the heating 
medium, again to be heated, and thus successively be 
fitted to suck moisture from soil, leaves, and stems, and 
it will easily be seen that, without counteracting agen¬ 
cies, our plants would soon be as debilitated by thus 
parting with their moisture, without an equal chance of 
absorbing more, as if they were exposed to the parching 
effects of a sirocco. Need we wonder that plants droop i 
from weakness, and that flower-stalks are too tender to ] 
support their burden! The more open the house the ] 
greater the danger from this cause; every volume of j 
heated air, loaded with moisture, that escapes, is re- ! 
placed in keen frosty weather by an equal volume of 
air, cold and nearly as dry as if it bad been baked in an j 
oven. If the pots are freely watered the remedy is more ] 
apparent than real: while the stems and leaves arc i 
being dried the soil and roots are being rapidly cooled i 
by evaporation, and that all the more if the pots, 
