THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Decembek 18, 1860. 
161 
house, with a fire from a living-room or kitchen on the other 
side are :—First, that there is apt to he too much heat in one 
place ; and, unless when extra well managed, though the back of 
the house may be even hotter than desirable, the front may be 
much colder than is wanted. There is a natural tendency in heat 
to diffuse itself until an equilibrium is gained; but as at the same 
time all heat ascends, it is apt to accumulate at the back of the 
house when the heating medium is there. It is true that the 
rays of heat from a stove at the back of a house not only 
ascend, but will be radiated towards the front of the house ; but 
just as from a fireplace in a large room, these rays will lose their 
force in proportion to the distance from the heating medium. 
In all places of any size, and where anything like continuous 
regular heat is desirable, flues are not only greatly superior to 
stoves, but when run chiefly along the front of the house instead 
of the back, the heat is not only more regularly distributed, but 
a thorough circulation of the air in the house is secured; as, no 
sooner does the ah* in contact with the heated flue become rare¬ 
fied and rise, than the colder air is brought to supply its place 
to be heated and rise in turn. 
For small solitary greenhouses, for forcing-houses of no great 
dimensions—say, 40 feet by 12 or 15 feet, standing by them¬ 
selves, I believe that good flues are still the best and the most 
economical mode of heating, and that the more these flues stand 
above the surface of the soil inside, and the nearer they are to 
the front of the house that convenience will admit of, the greater 
will be the power they w’ill exercise on the atmosphere of the 
house. On the principle of the ascent of heated air inside as 
well as outside of a flue, it is as well that the flue should rise a 
little from the commencement to the extremity where it joins 
the chimney. It is often necessary to make flues decline so as 
not to interfere with a pathway at a door, and, provided there 
is a high chimney at the back wall—say, ten or more feet in 
height, and the depression at the lowest point is fully a foot or 
more above the furnace bars, there will be a good draught; but, 
on the whole, flues will generally draw better when there is no 
dip in them at all, and extra draught can easily be regulated 
by a damper. When there is only one doorway in the end of a 
lean-to house, these dips and depressions may be avoided by 
sinking the furnace at the back sufficiently low* to allow the flue 
to pass under the pathway before rising into the house (see 
fig. 5), rounding that end, passing along the front round the 
other end, and going into a himney there, or returning by the 
back wall and entering a chimney near the furnace, as shown in 
fig. 10. The black lines are intended to show the flue and to be 
under the ground level until the doorway is passed at A. If the 
flue entered at the farther end, the furnace-bars need not be so 
much sunk, and then the flue might return in front, separated 
a few inches from the other as shown in the dotted lines in 
fig. 10. Where convenient this is a capital plan. It is usual to 
make turns in flues at right angles [_ ; tut it is better to make 
them rounded The heated air thus passes more freely. A 
rounding should also be given in the shape of an inclined plane to 
the flue as it comes from the furnace-bars. These bars should 
never be less than two feet from the bottom of the flue. (See furnace 
in fid- 5.) When there is no shed behind, the stokehole may 
be covered with a wooden flap-door. So far as mere working i6 
considered, the furnace may be at either end, or even in front as 
well as the back, though in all lean-to houses the chimney is best 
at the back, and in span-roofed houses it is best at the end. 
Now, when restrictions as to the form and size of bricks and 
tiles are removed, it would be easy to get material made on pur¬ 
pose for flues, and with covers especially made hollow so as to 
hold water. Until then bricks of the common size will be 
chiefly used, and for all forcing—not early, or where continuous 
heat, as in the case of the Pine Apple, is not wanted—bricks 
from two inches to two inches and a quarter thick, but all 
exactly of the same thickness, will answer well for sides and 
bottoms. 
For a seven-and-a-half or eight-inch-wide flue, inside mea¬ 
sure, we would proceed thus :— Mark out the base of the 
flue one foot wide, ram the ground well for a couple of feet 
in width, and if not sure of it put down four inches of concrete. 
If ground is firm do without that, then lay one course of bricks 
on bed, or on edge, on the ground level, and grout with good 
mortar; on that place a twelve-inch tile from one inch and a half 
to two inches thick, though thinner will do. This will form 
the bottom of the flue ; slate will do four yards from the furnace. 
On this build the sides with brick on edge, having previously 
damped all the tiles and soaked all the bricks, which should be 
new and hard-burned, and join them together with best lime 
putty and as small joints as possible, keeping the inside especially 
perfectly straight with no protuberances. A flue formed of 
four such bricks laid lengthwise and edgewise will be enough 
for a Peach-house or vinery not forced very early. The top 
should be covered with one-foot tiles neatly jointed. To prevent 
these joints giving way in forming the flue, it is as well to use 
firebricks for a yard from the furnace and to cover them with 
brick ; for four or five feet further the place might be covered 
with thin house-tiles, and after that with very thin slate chipped 
to the width of the outside of the flue. On these tiles and elates 
spread a thin layer of first-rate mortar, and on these place the 
top tiles. All the joints will thus be crossed, and there will be 
no chance of smoke escaping. If these tiles are hollow so as to 
hold water it will be a great advafl- 
tage i_j. The outsides might all be 
made two inches and a half or three 
inches in height, whilst the centre 
was only two inches thick. Such a 
flue would do for a late vinery or 
Peach-house 50 feet long, 12 feet 
wide, and 12 feet high, by merely 
passing through it along the front 
and both ends. If forcing was com¬ 
menced in January, the flue would 
have to return or be higher and 
three inches wider. If forcing in such 
a house was commenced in Novem¬ 
ber the furnace would have to be 
larger, and for fully the half of the 
length of the house w*e would build 
the flue as it came from the furnace 
with brick on bed instead of brick 
on edge, so as to equalise the heat 
more. In all cases where it is de¬ 
sirable to have a house 40 feet or 
50 feet long as hot or nearly so at 
one end as at the other, we should 
adopt this plan. The four inches and 
a half are so much longer in heating 
than the two inches and a quarter, 
that the heat is carried along. We 
have found this simple expedient 
answer all the purposes of re¬ 
served flues, and air-flues on the top of the others. We would 
have no plastering at all inside, as it is apt to be dislodged in 
cleaning, and, falling at other times, it is apt to cause an ex¬ 
plosion in the flue. Neither would we plaster outside if joints 
were sound. Where great heat was wanted, as in a chamber 
below Pines, &c., we would sooner use bricks their full length, 
