602 AllT OF GARDENING. P a r t III. B o o k I. FURNACES AND FLUES.
‘cockles ’ ra-oduciiiK tliat uneven puckered appearance wliich is the peculiar characteristic
of shcetlo-lass: and of these cockles some arc circular, and form lenses ot considerable
nowor ” “I’rom the preceding observations, it is quite clear that the use of sheet-glass,
UatcTOr may be its colom-, will always ho attended with some risk of injurmg the plants
grown under it; and tho reason why it burns in some places and in others docs not, is
also evident, as “all depends on whether tho leaves come within the foci of the lenses,
or whether such lenses exist in tho squares, some squares havmg lenses, and others not.
^Crow n-glass, as it can bo manufactured nearly equal to sheet-glass in stren^h,
is now generally preferred to it for horticultm-al purposes, as it prevents the formation
of lenses. Crown-glass cannot, however, be made so large as tho shoot-glass, the laigost
crown-glass being only about 9 in. wide, and from 20 in. to 22 m. long-. whereas the
sheet-glass may be had 33 in. long, and 12 in. wide, or even lai-gcr, if requisite.
2097. H a rtle i/s rough plate-glass is strongly recommended by Dr. Lindlcy. ihis
kind of glass,” he observes, “is made of the same materials as tho sheet-glass, hut hy a
very different process. Instead of being, in tlic first instance, blown into tlie form of a
cylinder, or ‘muff,’ then slit and flattened—a diflicult process, incapable of making it
level or free from largo irregular lenses, — rough plate is at once rolled into plates, and
left with an irrcgtilar gi-.anulatod surface, which breaks, and bends, and separates the rays
of livht as tlioy pass throngh it, tlms rendering thcir concentration, and the burning con-
MLntiiponiqimpossib? (C a rd . C hron. fo r 1849, p. 116.) Another advantage oi
this kind of glass is that it does not rcqmrc shading
2098. T h t sash-fram es o f lights ai-c very apt to become twisted, when the panes of
glass are of a very lai-ge size ; and when this is the case, the glass is not only liable to
bo broken, but tho frames will not fit close. On this account it is now generally recommended
that no panes of glass should he used for horticultural purposes which arc larger
than 9 in. wide by 18 in. long, and that tlic tliickness should not exceed 18 oz. to the
foot In oases where tho sashes have to bo shifted fi-cquontly, even this is found too lai go,
and it is said that the panes of glass should never exceed 7 m. or 8 m. m width, and
'**2™9 ™ TF/Sre sm all panes o f glass a rc used, common sash glazing is generally performed
with a lap of from one fourth to tlircc fourths of an inch, and the space between the
panes of glass is generally flUed up with cither putty or lead. A mode, however, was
suggested in the Gardeners' C hronicle for 1844, of having the glass of each pane cut
with a perfectly straight edge, and placing them so that they shall aU
“When the light is completed, the surface of the glass is perfectly level and there aie
no interstices in which the dust, &c., can accumulate, or for the deposit of moisture,^ liy
this means, one cause of considerable breakage iu frosty weatlier is entirely avoided ;
and if a pane of glass bo accidentally broken, the fracture does not necessarily extend
beyond that pane, as each pane is independent of the ottos. Tlic wliolo is very fiim
and compact, and the glass is not liable to shake out. ( /. L . S n ow m the Gmd. Chron.
for 1844 p 277.) According to the old mode of glazing, the panes m hothouse roots
had fi-eqiiontly laps a full inch broad. Nothing could bo worse tlian this plan ; as tho
broader tho lap, the greater was the quantity of water retained m it by capillaiy atti-M-
tion • and when such water, from a deficiency of heat in the house, became fiozcn, the
glass was certain to be broken. In other cases the broad lap soon fi led up with earthy
matter, which was not only unpleasant to the eye, but injurious, by obstracting the light
MLazmq c u rvilin e a r houses, it is necessary either to anneal and bend the
glass or StiU to use small panes; and, in tho latter ease, it is considered best to throw the
panes into triangles. By adopting triangular panes, tho most singular- shaped roofs may
be glazed as perfectly as the simplest forms of surtace.
2101. Though the m aking o f p u tty I x hardly withm the gardeners provinoo, yet it
is fitting he should know that there are several sorts, of which the following are the
principal: —
S o ft v u tty , b e in g a w e l l -w r o u g h t p a s t e o f f lo u r o f w h i t e n in g a n d r aw l i n s e e d - o i l ;
c o m p o s e d o f w h i t e n i n g a n d b o i l e d l i n s e e d - o i l ; j i n
H a rd e r v u ttu in w h i c h a p o r t i o n o f t u r p e n t i n e , o r w h a t i s c a l l e d d r y in g o il, is i n t r o d u c e d ; a n d t h e
H a rd e s t p u tty , c o m p o s e d o f o i l , r e d o r w h i t e l e a d , a n d s a n d . T h e l i r s t i s t h e m o s t d u r a b l e o f a 1, b c -
c a u s ? I t f o rm s a n o l e a g in o u s c o a t o n t h e s u r t a c e , b u t i t r e q u i r e s a lo n g e r t im e lo r d r y in g . 1 h e h a r d s o r t s
a r e a p t t o c r a c k , i f n o t s o o n w e l l p a i n t e d ; a n d t h e h a r d e s t o f a l l , th o u g h i t a p p e a r s to b e im p e n e t r a b l e ,
a n d o f t h e g r e a t e s t d u r a b i l i t y , y e t r e n d e r s i t d if f ic u l t to r e p l a c e a p a n e w h e n b r o k e n . I t s e em s , th e r e f o r e ,
o u i t e u n f i t f o r h o t h o u s e s . M u c h d e p e n d s o n w e l l w o r k m g t h e p u t t y s o m e d a y s b e f o r e i t i s to b e u s e d ;
2 n d , in g e n e r a l , t h a t p u t t y w h ic h h a s b e e n g r o u n d a n d w r o u g h t i n a p u t t y -m i l l i s to b e p r e f e r r e d .
S u b s e c t . 5. W a lls o f Hothouses.
2102. W a lls of some sort arc necessaiy for almost every description of hothouse; for
even those which arc formed of glass on idl sides arc gcneraliy placed on a basis of
masonry. But as hy fur the greater number ai-c erected ibr culinary purposes, they arc
])Iaccd in the kitchcn-gardcn, with the up[)er part of their roof leaning against a wall,
w'hich forms their northern side or boundary, and is commonly called the back -wall, and
the lower part, resting on a low range of supports of iron or masonry, commonly called
the front wall.
2103. T he p a ra p e t, o r fr o n t w a ll, of hothouses comes first in order. Where upright
sashes ai'C used, there arç generally brick walls, either carried up solid from the foundation,
or built on piers, according as it may be desirable to have the roots of the plants
within pass through to the soil without, or not. In the case of fixed roofs, that part of
the wad which is above ground is formed with horizontal openings, to wliich opaque or
glazed shutters arc fixed, opening outwards, for the pui-pose of admitting air.
2104. H oles f o r vine-stems. In all parapets or front arrangements where vines arc to
be introduced from witliout, particular care must be had to provide for the withdraaving
of tlio vines, even when thcir wood is of a considerable age and thickness. For this
reason, where horizontal shutters arc used, the lower styles or pieces against whieli they
shut should always be movable ; and, in general, it may be stated, that of the various
modes for the introduction of the vine from without, which have been adopted, that by
cutting off a corner of the sloping or front sash is the best : by this means, when the
sash is opened, a vine of almost any size may be taken out with case. A [)iece of thin
board or cork cut every year to fit the increasing diameter of tlic shoot is screwed to the
wall-platc or Icwcr style, as the ease may be, and the vacuity, which must necessarily he
left around the stem, is closed up with moss. When tho vine is to be taken ou/_ by
unscrewing the triangular board, and opening the sash, or shutter, a more than sufficient
.space for drawing out any ordinary-sized jilaiit is obtained, without the least trouble or
chance of fracturing the shoots.
Subsect. 6. F urnaces and F lu e s.
2105. Th e oldest mode o f heating hothouses is by fire s a nd smoke-flues ; and on a small
scjile, it is still used occasionally. Heat is the same material, howcA'cr iiroduced,
and a given quantity of fuel wiU produce no more heat when burning under a boiler
than when bumiiig in a common furnace. Hcncc, with good air-tight flues formed
of well burnt bricks and tiles accurately cemented with limc-putty, and airangcd so as
the smoke and hot air may circulate freely, every thing in culture, as far as respects heat,
may be pci-fcctly accomplished.
2106. T he hothouse firep la ce , o r fu rn a c e , consists of several parts : a chamber, or oven,
to contain the fuel, surrounded by brickwork, in which firebricks (bricks containing u
large proportion of sand, and thus calculated by their hardness not to crumble hy heat,
&c.) arc used ; a hearth or iron grating, on wliich the fuel is laid ; a pit or chamber
in which tho ashes drop from this grating ; and iron doors to the fuel-chamber and
ash-pit.
2107. A s to the size o f hothouse fireplaces, the door of the furnace may be from lOin.
to 1 ft. squai-c ; the fuel-chamber from 2 to 4 ft. long, from 18 in. to 2 ft. wide, and of the
same dimensions as to height. Every thing depends on the kind of fuel to be used. For
Newcastle coal, a chamber 2 ft. long, 18 in. broad, and 18 in. high, will answer as
well as one of double the size, where smoky Welsh or Lancashire coal is to be used.
Various contrivances, as hoppers, horizontal wheels, &c., have been invented for supplying
fuel to furnacc-fires without manual labour, and especially durmg night ; but, from the
nature of combustion, and the common materials used in this counti-y to supply it, no
effectual substitute has yet been discovered. If wood or chai-coal, or even cinders or
coke, were used, there would be a greater chance of such inventions succeeding ; hut we
do not think ourselves warranted in detailing any of them.
2108. T he modes o f constructing flu e s are various. The original practice was to build
them on the naked eai-th, like drains or conduits ; or in the solid walls of the backs and
fronts of the pits, like the flues of dwelling-houses. The first improvement seems to have
been that of detaching them from the soil by building them on flag-stones, or tiles supported
by bricks ; and the next was, probably, that of detaching tliem from every description
of wall, and building thcii- sides as thin as possible. A subsequent amelioration
consisted in not plastering them within, hut in making thcir joints perfect h y lime-putty,
by which means the bricks were left to exert thcir full influence in giving out the heat
of the smoke to the house.
2109. Th e sides o f common flu e s are commonly built of bricks placed on edge, and the
top covered by tiles, cither of the full width of tho flue outside measure, or one inch
nairowcr, and the angles filled, up with mortar, which Nicol prefers, as neater. Where
a stone that will endure fire-hcat witliout cracking is found to be not more expensive
than tiles, it is generally reckoned prelcrable, as offering feiver joints for the escape of
the smoke. Such stones arc sometimes hollowed on the ujipcr suriacc, in order to hold
water for the benefit of plants in pots, or for steaming the liouse.