The class of apparatus to be adopted in any country will vary with the climate. In England the climate is of so very changeable a nature, that the amount of heat required for comfort in a house varies from day to day. There are many days in the middle of winter when it is quite possible to sit in an unwarmed room; or, sometimes a warm morning is followed by a cold afternoon, when the sudden application of heat is desirable. It is probably for this reason that in England the open fireplace has, as a rule, held its own against all the proposals for warming houses by means of one central fire.
The open fireplace in ordinary use warms only by means of the direct radiation of the flame into the air of the room. It is the most primitive mode of warming, derived from the days when our ancestors inhabited caves. But these ancestors, by placing the fire in the centre of the floor of the cave, derived from it a larger portion of heat than we generally do, who place it against the wall of the room, and carry off the greater part of the heat up a flue separated from the room. The earlier fireplaces consisted of a large square brick opening, with a chimney carried up for the escape of smoke. The large square fireplace was adverse to the direct radiation into the room of the heat generated, and the large chimney removed from the room a very considerable quantity of air, which had necessarily to be replaced by cold air flowing into the room through all available apertures, and this created strong draughts.
Franklin, Count Rumford, and Sylvester, are the most prominent names of those who at an early period contributed improvements to the warming of our houses. The main principle of fireplace construction advocated by Count Rumford, eighty years ago, was, that the heat radiated from the fire directly into the room should be developed to the utmost. He brought the back of the fireplace as prominently forward as possible; he sloped the sides so as to reflect heat into the room; he advocated the use of fire-brick backs and sides instead of iron; he reduced the size of the chimney opening, so as to prevent the chimney carrying off the large quantity of warmed air it used to remove in his time. Our manufacturers of fireplaces have continued in the same groove. They have, undoubtedly, in some cases, largely developed the use of radiant heat. There are fireplaces, eminently successful as radiators of heat, of a circular or concave form, with polished iron sides, the fire being placed against a fire-brick back forming the apex of the concavity. So long as the concave surfaces are bright, the heat thrown out by them when a clear flame is burning is very great, but the gases from the flame pass directly off into the chimney while they are still at a very high temperature. The heat of the flame at that part will often be between 1,200° and 1,300° Fahr., and a very large proportion of this heat, to the extent of at least nine-tenths of that generated by the combustion of the fuel, is carried directly up the chimney.
