THE COTTAGE GARDENER AND COUNTRY GENTLEMAN’S COMPANION, January 13, 1857. 
259 
the actual furnace or fuel box; in part of their length, 
where such is the case, they are built of fire bricks, as are 
also the flues; and wherever the walls are likely to be much 
heated, they are Stourbridge fire-bricks set in the same clay, 
being, in my opinion, more durable than Welsh lumps ; it 
will be well to parge the outside of the walls of the stove. 
The stove is 3 feet high, which allows 3 inches for paving 
of ash-pit + 1 foot for depth of ash-pit + 3 inches for depth 
of bars + 1 foot (1 inches for depth of furnace from bars to 
plating = 3 feet. The iron top is formed of three plates, 
with a view to allow of expansion ; two of these plates have 
extending rabbets, so that when laid in place they have this 
appearance. 
They are 1 foot 6 inches one way by 3 feet G inches the 
other, so that when laid in their place, and the space for 
expansion between each allowed, they form a surface of 
4 feet 7 inches by 3 feet 0 inches. This, by calculation, will 
bo found to give them a 4-inch bearing on the four outside 
walls of stove. Along the wall of stove next the hothouse 
a course of thin brick is laid, not close to the edge of plating, 
but half an inch from it. The two end walls are carried up 
three courses higher in 4^-inch work, and so also the outer 
wall; and between all these and the edge of plating there is 
i a half-inch space; the purpose of this groove is to fill it 
with sand, so that the plates can expand and squeeze up the 
sand, while, when they contract, this will follow back and 
keep the joint air-tight. I am assured, however, by practical 
! men of great experience, that it will be found quite un- 
' necessary to have the plates cast in three pieces; that it 
I would suffice if cast in one piece, provided it were cast with 
a loop round the edge, which should fall into a groove of 
sand, and that the plate would then expand in the loops : 
this will greatly lessen the danger of exhalation. The 
' situation of the damper, as shown in section, is bad; it 
i should be placed exactly at the junction of the flue with the 
] chimney; and it will be found to economise fuel, by pre- 
| venting the loss of heat, if between the brickwork forming 
| the end of chamber and the stove some non-conducting 
! material, such as hair-felt, be placed, and also if double doors 
be used for the furnace. I find the only loss of heat that 
j takes place in the apparatus at Nutfield is from the furnace- 
i doors and the bricks around them, and this might be 
prevented by the above plan. The doors employed are 
1 Sylvester’s patent, which, for all purposes where the 
regulation of draught is required, seem to be tbe best that 
can be imagined; there are no hinges to rust, or machinery 
[ to get out of order, or screws to untwist; they simply hang 
on a frame, in which they slide, the edges of the door and 
| frame being ground to fit; and another advantage which 
i they seem to me to possess is, that if any explosion should 
take place within the stove, from a collection of gases (and 
all economic stoves, where of course the combustion is slow, 
are liable to such occasionally), instead of the boiler or 
plates being blown out of their place, these doors would be 
lifted outwards, and the evil consequence avoided. Within 
the chamber, extending between the two end walls of the 
stove, and bearing slightly on the end wall of the hothouse, 
is a tank of water, E, divided longitudinally, four inches deep, 
as shown in section, also by dotted lines in ground plan, 
supplied by a check cistern from tbe outside, G, also of 
I course divided; this may be furnished with a tap, by which 
j to empty it, or at which the gardener can always obtain 
| chilled water.* The roof of the hot chamber is formed of 
| double slating, with a layer of M'Neil’s hair-felt and two 
or three inches of sawdust between, and the upper surface is 
never warm. From these arrangements it is evident that 
the entire air of the hothouse must flow over the plating, 
through the chamber, and back over the tank of water (as 
* This cistern or tank is of very unnecessary extent. It is five feet 
long by three feet six inches wide. If it were eighteen inches or two feet, 
it would be ample to supply the moisture necessary, and this should lie 
divided as in plan. For a conservatory, a single trough nine inches wide 
would be amply sufficient, and even this, as fires are only required in 
such structures in winter, when much moisture is not required, would 
almost be unnecessary. It will be observed from the position of the tank, 
that its under surface forms a sort of roof to a flue, compelling the cold 
1 air to traverse the hot plate before returning to the house, so that if the 
j tank is dispensed with, some other means must be taken to secure this, 
such, for instance, as a sheet of iron plating or thin casting. My present 
tank will evaporate fifty gallons per week. 
shown by the direction of the arrow in plan and section), 
and be returned back into the hothouse in a heated form 
through the upper opening. Here it is received into a large 
brick pit (as shown by inner lines in plan), and it is allowed 
to escape through slate ventilator’s from the sides and end 
of this pit. Iron bars extend across this pit, and on these 
slates (thick duchess) are laid; upon these some pebbles 
and a few inches of tan as plunging material. To those 
who have been accustomed to hot water I may say, that if 
they regard the cold-air main drain as tbe return-pipe, tbe 
chamber as an air-boiler, the brick pit as a hot-air tank, they 
can be at no loss to understand either the an-angement or 
the principle, and to perceive that there is no difficulty 
whatever in reducing those principles to practice. And 
this brings me to the third consideration I had proposed, 
namely, the advantages likely to result from the employment 
of Polmaise heating ; and the relative importance of these 
advantages will be differently regarded by different classes 
of persons. The wealthy lover of horticulture will first in¬ 
quire, Can I grow my plants better? He who is equally 
fond of it, though with less means, will inquire first, Can 
I grow more cheaply ? while the grower for profit will 
consider both of equal importance. I will consider cost, and 
first the original cost: this will be regulated by the purpose 
for which it is required, similarly to other heating powers. 
An apparatus of equal power with mine may be erected for 
£20, dependent on the price of brick and slate. It must be 
considered that for this sum a great amount of bottom-heat 
is secured, from 83° to 94° Fahr., over a bed twenty-two feet 
six inches by nine feet wide, together with the requisite 
amount of atmospheric heat in a house twenty-eight feet by 
seventeen. Compared to hot water, I am sure the first cost 
does not exceed one-half what the latter would be to secure 
the same amount of bottom and atmospheric air in the same 
house in the same locality. But the way in which the economy 
is best viewed is by considering that the entire expense of 
the distribution of the heat is necessarily saved by the air 
distributing it by its own motion, and that the expense of 
the air-boiler and setting is about the same as the water- 
boiler and setting; the expense of the tank it is fair to 
charge not to the heating but to the evaporation, as moisture 
must be supplied in some way under any mode of heating. 
The working economy I take to be equally certain. If the 
stove is properly built there need be but little loss of heat, 
the heat of the stove being all swept into the house by the cur¬ 
rents, except that portion which is lost at the junction of the 
stove with the external wall of chamber ; while in the hot- 
water apparatus, if the boilers are set externally (and it has 
not been found advisable to set them within the house), there 
is great waste of heat,—I do not speak of every individual 
case, but of the generality of cases ; and since a given 
quantity of fuel can only evolve a given quantity of caloric 
during its combustion, it is quite evident that that system 
must prove most economical in the use which secures the 
most caloric for the purpose required. With regard to the 
amount of caloric passing up the chimney, Polmaise stands 
on the same footing with all other economical stoves in 
which the combustion of the fuel is regulated by the supply 
of the oxygen and by means of Sylvester doors, and dampers j 
in the chimney; the amount of heat lost in this manner is 
inconsiderable. Some heat must always be sacrificed in this 
manner in all systems; for if there were no caloric in the 
chimney—that is, if the air in the chimney were not rarefied— 
there would be no current of air to the fuel, and tbe fire 
would not burn; and if this is to be saved, it can only be 
done by bringing the chimney through the house,—in fact, 
by again returning to the fiue system. 
Having noticed the advantages of Polmaise heating, I 
have no wish to conceal its dangers. Man may take the 
principles of Nature, and when he reduces them to practice, 
he finds that he has introduced some human imperfection, 
and so it is with Polmaise. A boiler may burst, or a pipe 
choke up with a hot-water apparatus, and a gaseous ex¬ 
halation may escape from the stove of Polmaise. The com¬ 
pounds of sulphur and oxygen appear, even when much 
diluted, most prejudicial to vegetable life, and the effects of 
the bursting of a flue are well known ; and this is the point of 
danger. I prophesy that no winter, however severe, will 
affect the operation of Polmaise; but all the beauty of this 
principle of heating must be sacrificed unless we can secure 
