THE COTTAGE GARDENER. 
201 
June 27.] 
and-water-tight joints not allowing any escape; and if 
we had the same amount of heat, I cannot see where it 
would differ in its component parts from heat derived 
from confined water, inasmuch as both substances are 
alike shut out from access to the atmosphere of the 
house, that we must look to other causes for the differ¬ 
ence which exists. 
In the first place, smoke is seldom honoured with a 
cast-iron pipe to travel its rounds in, neither is it neces¬ 
sary that it should he so, when a cheaper material can 
be had. The only place where I did see it in use, seem¬ 
ingly acted no better than an ordinary brick flue; and 
as its great expense will ever prevent its being generally 
adopted, I will, in the present chapter, endeavour to 
compare the merits of a good ordinary smoke flue with 
that of a well-arranged boiler and pipes, and make such 
remarks as a long course of experience lias placed within 
my reach; so as to enable the amateur, about building 
a greenhouse or a grapery, to judge for himself which of 
the two systems will most likely suit him. I put Pol- 
maise out of the question, because it seems abandoned 
by all but those who committed themselves so much by 
lauding it, as to be unwilling to retract their opinion. 
Before comparing the two competing systems, it may 
be better to say a few words on smoke flues, as disap¬ 
pointment sometimes arises from them ; but very little 
need be said. Generally, circumstances over which we 
have no control fixes the place where the stoke-hole 
is to be. When a choice exists, let it be as much as 
possible exposed to the open air. The best acting fires 
I ever had of that description had no shed or root over 
them, and, by the nature of the plan, were not at all 
sunk below the surface; but it is generally necessary to 
sink the fire hole, that the smoke in its course may first 
ascend a little, otherwise travel on a level. It is very 
unwilling to dip downward on its first formation, but 
after once entering the flue and travelling some distance 
it may be made to descend then very well, only such 
descent had better be gradual and not in sudden per 
pendicular falls. There are many cases, as the crossing 
of a door-way, when it is necessary to sink the flue. In 
that case let it be done gradually as an inclined plane ; 
and be not satisfied by making the bottom of the flue in 
that way, but let the top, or cover, be made so likewise, 
because smoke invariably floats on the top or upper side 
of the flue, and I think but seldom expels the whole of 
the atmospheric air over which it rolls. Now, as such is 
the case, a sudden obstruction, as a mass of descending 
brick-work, offers exactly the same impediment to its 
onward course that a mill-dam does to that of a river, 
save that the latter is irresistible ; but the accumulation 
in both cases is the same, and in the case of the flue 
offers a powerful check to the impetus which directs it 
forward. Therefore, smooth it off; and if the appear¬ 
ance requires it to assume a perpendicular fall, let that 
be done by building upon the flue so made the required 
height. It will so much certainly impair its efficiency 
by burying the heat, but if every other circumstance be 
favourable, little loss will be felt. 
For the same reasons as above let all the corners or 
turns he rounded, so that every facility be made for the 
quick circulation of that heated air we so often call 
smoke; and when it has travelled its rounds let it have 
a few feet of upright chimney through which to make its 
final escape. 
In the erection of a flue use the best bricks. The end 
nearest the fire of the side-walls of the flue ought to be 
half brick thick, that is, inch work; the remainder 
may be brick on edge, and only those near the fire need 
be fire-bricks; the covers also near the fire ought to be 
of that material. Cement, or what bricklayers call 
“ compo," ought not to be used. It does not stand the 
fire well. A flue, about 9 inches wide inside by about 
12 inches deep, will be ample size for most purposes, and 
one much less than that will not be found to answer well 
long. I may as well add, that flues of all kinds ought 
to stand above the level of the ground-work of the house, 
and not be buried under the walk, as is too often the case, j 
Of course, many circumstances place its direction in a ; 
certain way inevitable ; but when a choice can be made 
let it be as much as possible exposed, only not so as to j 
endanger its taking harm from its improper use as a stand 
for plants, without duly guarding it by a trellised shelf 
resting on iron bearers, or such like. 
Amongst the many supposed advantages liot-water 
pipes has over a flue,the consumption of fuel is one; yet 
the difference is often over-stated. I do not deny but 
that a well-constructed hot-water apparatus will heat a 
given space with less fuel than a flue will do under some 
circumstances, but there are cases again the reverse,— 
where a large old house, indifferently glazed, is heated 
with hot water, it will he found almost impossible to 
maintain a forcing heat, unless there be a great number 
of pipes employed: the reason is obvious. Water will not 
heat beyond the boiling point, 212°, it passing then off 
as vapour; now a flue maybe heated much beyond that, 
but such cases are of rare occurrence, and I only refer 
to an extreme case to illustrate my views, that unless an 
ample provision of pipes be made a flue is safer in a 
severe frosty night. 
That flues use more fuel in a general way I at once 
admit, and having had a considerable share of experi¬ 
ence in the management of both plans, I should say 
that such difference may amount to one-lialf; it is not 
very easy to make calculations of that kind with any de¬ 
gree of accuracy, but certainly it does not exceed that; 
the amount of labour and attention is certainly much 
less on the side of the flue than on that of those fan¬ 
tastic contrivances of boilers, but on well-constructed 
apparatuses the attention is about alike. 
In regard to the quality of the heat evolved, there is 
much difference of opinion; certainly where a flue has 
been long out of use, a disagreeable smell arises when 
the fire is first lighted, doubtless as offensive to the 
vegetable kingdom as to ourselves; but it is soon all 
right again, and if one or two ventilators be thrown 
open, the place is soon sweet. The reason of such a rank 
smell is the dissipation of those vaporous gases which 
are generated by heat applied to the damp brick-work; 
that hot water pipes are free from that evil is certainly 
a point in their favour, yet it must not be valued too 
highly. 
Acknowledging the above two points to be in favour 
of hot water, let us examine the claims of the flue, and, 
the first thing, compare the respective cost of the two ; 
and I am certainly within the mark when I say, that the 
flue will not cost more than one-tenth or one-twelfth of 
the other system, and that is a very important matter. 
It is of no use being told you will save it all in the end 
by the less fuel wanted; I have known an apparatus of 
that kind cost as much as would have built a flue, and 
supplied it with coal for twenty years ; and that was not 
an unusual case. If the amateur be building a small 
house, and decide on having pipes, &c., he may rest as¬ 
sured the heating apparatus will cost him as much as 
the house altogether (provided there be no architectural 
ornaments, &c., about it); and if he be building two 
moderate-sized ones, the cost of boiler, &c., being less, 
will probably be about two-thirds of the expense of the 
whole of the work. I mention these matters because I 
know many people forget the expense of heating when 
they take the building matter in hand. Now, suppose 
a greenhouse was wanted, 30ft. by 15ft., and about 12ft. 
high, let us say that such a house cost .£80, now it 
would seem foolisli to throw away £00 or £70 more in 
an apparatus to heat it the few times that it might be 
wanted in winter to keep the frost out, when the same 
purpose could be effected by £5, or, at the most, £8; 
