GO 
THE COTTAGE GARDENEB. 
October 27 
being equal, will be move boated by the sun in summer, 
and cooled by tbc frost in winter, than ground turned up 
rough and full of air. The more porous and open a body, 
the less its radiating and conducting powers. Thus, "a 
cover made of wool, hair, &c., would retain more beat 
than one made of vegetable fibre, packed close together; 
inasmuch, as in the first case there would not only be I 
the interstices between the threads, but every hair would 
be a hollow tube. The great advantage of a non-con- * 
ducting material impervious to water, is not only the 
preventing cold rain getting to the glass, but keeping a 
porous body from being partially changed into a dense ! 
one. In a frosty night, a dry cloth, or a dry mat, elevated 
a little above the glass, would have a more beneficial 
effect than a wet mat or cloth clinging to the glass. In 
the latter case, cover and glass soon become as one sub¬ 
stance, so far as preventing radiation of beat is con¬ 
cerned. This takes place not merely on account of their 
contiguity, but because the porousness of the material has 
been destroyed by every air opening being solidified into 
ice, or, at least, filled with water. In the latter case, ! 
when the air is not so very frosty, but clear and dry, 
there is also the loss of heat by evaporation, in addition 
to that from radiation. 
Something would be gained, wore it ever kept in 
mind that the evaporation of moisture from any ' 
body produced cold or a diminution of heat in that ! 
body. A dry surface, or one such as painted wood, J 
that will not absorb much moisture, is therefore of 
great importance. Railing that, bodies open in their 
texture, or that consist of hollow tubes, such as wool, 
hair, hay, and straw, are better than more close and 
compact bodies. This will further appear, if what I ! 
stated last week of the non-conducting properties of 
confined air be taken into consideration. It is difficult 
to completely isolate a body of air between the glass and 
the cover; but the more it was done, the more perfect it 
would be. Even when not isolated, this body of air is 
of great advantage; as not only is there a radiation of 
beat from the upper surface of the covering, but there is 
a double process of radiation beneath it; the glass 
radiating to the cover, the cover radiating back again to 
the glass. In fact, the same process is going on that 
prevents the surface of the ground being sufficiently 
cooled to be (Jeuecl in a cloudy night of autumn. The 
cloud is the cover that radiates heat back again. When 
we enclose a quantity of dry, tubular, porous matter I 
between the glass and the cover, the same process goes 
on. Hence, I have seen one man keep up heat, with 
more trouble, and using four or five thicknesses of mats, j 
than another man would manage without any trouble at 
all, by merely having a cloth or mat on the glass to keep J 
it clean; a little clean litter thrown over it, and a mat 
or waterproofed covering thrown over all, to keep it in 
its place, and preserve its dryness. As our friends seem 
all to make a point of cheapness, in all cases of low 
pits, where litter is plentiful, and the appearance of the J 
glass no object, the throwing on of this litter, and pull- 
ing it down in the morning with the back of a rake, is j 
the cheapest ot all, though rather littery indeed in its 
working. However, many would see no unsightliness 
where there was a seen and felt utility. 
baking, however, all these matters into consideration, 
holding the perfect propriety of recommending what we 
believe to be best, though we may not be able to show 
that very plan exemplified in our own practice, not 
forgetting neatness as a calculation about a garden, and 
looking at expense, not as spread over one year’ but 
over some six or ten years, I still consider, notwith¬ 
standing the remonstrances of some friends, mats to be 
the dearest and most littery coverings ; and wooden 
coverings, made of three-quarters or an inch best deal, 
with a ledge all round, fully an inch deep, to raise them 
thus farther from the glass, and made to lit close to 
each other, as ultimately the cbeupest and best. Thus, 
supposing that for a common-sized light of a pit, say 
lour ieet by six or seven, a wooden shutter would cost 
about 7s.; a good mat, according to the statement 
of a London nurseryman, the other day, would cost 
from Is. (id. to Is. ibd. this season, which seems very 
high. Well, that mat, with plenty of litter over it, 
would keep out frost, but then that would be unsightly, 
and a double one, as a cover all, would probably be re¬ 
quired. If you commenced now, you might ask, Where 
these mats were next July? and echo would tantalize 
you with Where.” The same supply would be required 
the following year; and thus, with double mats, which of 
themselves would not be one-third so sufficient as the 
wooden shutters, in two years, if you counted the trouble 
of tying the mats, hanging them out to dry, &c., you 
would have pretty well paid the price of a shutter, and 
have nothing to look at for your money; while your 
shutter is as good as ever, and takes no more trouble 
from you than putting it on and taking it off. You 
say this is not fair, because the mat is larger than will 
cover a common light. Well, then, take the case of our 
friend with his pit 40 feet long, and 0 feet wide, at 
least the glass is that width. Now, supposing each 
mat to be about 71 feet long, and 41 feet wide, two of 
these placed lengthwise will give the" width of the pit, 
and twelve mats would cover it altogether, with some 
feet to spare at the ends. These, without counting 
carriage, tying, drying, &c., would cost from 18s. to 20s. 
Ihese single mats, however, would only be sufficient 
in a sudden slight frost of a few degrees. To keep out 
a sharpish lrost, you must either use great quantities of 
litter, or double or triple mats. These mats would be 
the best things to get in an emergency. Now, suppose 
you paid as much as 10s. even for a wooden cover for 
such a wide pit, and that ten of these were necessary, 
which might be safely calculated upon to last ten years, 
and longer, if well used, the single mat alone would 
cost the price ot the wooden cover in five years, the 
double one in two-and-a-half years, and if leaving the 
litter out of view, we reckoned the small sum of 10s. 
each year for tying and drying mats, then, as in the 
former case, the mats would cat up the price of the 
substantial covering in two years, and never be a good 
protection after all. 
“ But as mats are cheap, could they not be rendered 
waterproof, and thus be made more lasting and effec¬ 
tual? \es ; but not so as you can roll them well. 
They must be fixed upon a frame of wood. You could 
not make a secure skeleton frame of wood, on which to 
tack the mat securely, under Is. (id. to 2s. This, with 
a single mat, would be half of the expense of a wooden 
covering. When such a mat, however, is brushed over 
with tar, and then well daubed with dry sawdust, it 
becomes waterproof, the frame raises it from the glass, 
and it will be a good protection for several years; not 
much inferior, while it lasts, to Asphalt-felt, while the 
first cost will be from one-half to two-thirds of the felt. 
The Asphalt-lelt being sold at Id. per square foot, is 
consequently 9d. per yard. It cannot, however, be used 
for the purposes of protecting pits before it is fixed to 
a substantial frame to slide up and down over the 
sashes. That frame would cost, at least, from !)d. a yard. 
The cover, when finished, would be as nearly as 
possible two-tliirds the price of a wooden cover. I 
know that with proper care, and giving the upper 
surface a slight coat ot tar every summer, such covers 
will last a number of years, and be cheaper in the end 
by far than mats, though at first it bo double; and when 
fixed to a frame, nearly four times the price of the same 
measurement of the common detached single mat. 
It has been urged against all these frame-covers, that 
sliding them over the sashes injures the paint; and that 
more than ono man is necessary to take them off and put 
I 
j 
I 
