62 
IRON AND WOOD ROOFS FOR STOVES, &c. 
ing and making up the fire the last thing at night ; for it is impossible for any man to 
manage a fire properly with a furnace door (such as is used for some apparatus) that 
does not exceed six or seven inches square ; but if a good-sized furnace door is used, 
the gardener is enabled, in countries where coals are dear and wood plentiful, to 
burn logs of wood, or the refuse from the pruning of trees, when he only wants a 
little fire through the day ; but of course it must be understood that this descrip- 
tion of fuel is not to be depended on in severe weather, nor for making up fires for 
the night. Whatever description of fuel is used, however, I have always found it a 
great advantage and saving to gentlemen to have a moderately large furnace door ; 
great attention being paid to its formation in order to prevent the passage of air 
through the furnace door between the boiler and the fire, the neglect of which 
causes a great waste of caloric or heat, as air will not support combustion until its 
temperature is raised to 800° or 900° Fahrenheit ; therefore a current of cold air 
admitted between the boiler and the fire through the door has a tendency to coun- 
teract the power of the fire, to obviate which double doors should invariably be 
used, and then if the boiler is so constructed and set as to expose (which is the 
great secret in the formation of all boilers) a large surface to the action of the fire, 
by means of the construction of the flues round it in such a way as entirely to 
consume the whole of the caloric or heat before it escapes at the chimney, the 
greater will be the saving of fuel, and the more powerful and effective the opera- 
tions of the apparatus altogether. Between the door and the fire there should be 
a piece of iron one foot three inches by one foot wide, which acts as a carbonising 
plate, and when the fire begins to burn strong so as to heat the iron hot, nearly 
the whole of the smoke is consumed. Indeed I have no hesitation in saying, that 
if a proper quantity of pipe is used so as to give a sufiicient quantity of surface for 
the command of temperature required in all extremes of weather, and the furnace, 
boiler, and flues, being constructed as suggested, the fire might be made up and 
left without the least risk for six or eight hours on the severest nights. In the 
formation of the egg-shaped holler^ my attention was particularly directed to the 
construction of a furnace that would obviate the evils complained of in most hot- 
water apparatus : I mean the great consumption of fuel, and the almost constant 
attention required, all of which arises from badly-constructed fire-places and 
boilers ; but then there are several other circumstances connected with hot-water 
apparatus which I think highly necessary to be attended to, particularly when the 
boilers are formed of series of pipes varying from half an inch to two inches 
in diameter ; for in the first place on no account should dirty water be used, as it 
causes a settlement or accumulation of mud, which in time not only injures the 
boiler, but lessens its power, not only by preventing the fire from acting imme- 
diately on the water, but also because the accumulated deposit impedes the circula- 
tion of the fluid by diminishing the calihre of the water way, and ultimately forms 
a hard incrustation similar to what is seen on the bottom of steam boilers, and it 
frequently ends in burning a hole in the boiler. Sometimes, in order to save a 
