WARMING AND VENTILATION. References having been made from SMOKE, Srovz, and VENTILATION to the present article, it will be desirable here to glance rapidly at the principal modes em ployed for warming and ventilating buildings generally.
Open fire-pla-ces.—A " cheerful English fire" is associated with so many ideas of comfort and social enjoyment, that we are apt to forget how dearly we pay for it. Dr. Franklin and Count Rumford did some thing to call attention to the subject, but Dr. Arnott has done more. In order to understand this matter, it will be noceimary to bear in mind that, while some fire-places or stoves give out heat by conduction chiefly, others do so mainly by radiation. Open fire-places are of the latter kind, and a serious loss of heating-power results from the arrangement.
The burning coals radiate heat into the room, and another portion of heat is reflected from the metallic portions of the grate ; but the heated air, which ought to contribute to the desired effect, is mainly allowed to escape up the chimney with the smoke and other results of combustion.
Dr. Arnott enumerates about a dozen evils which are more or less inseparable from the familiar open fires of our apartments. Among these are : Waste of fuel.—There is, first, the heat which escapes with the smoke; then the current of warmed air from the room, which ascends the chimney ; and, lastly, the valuable fuel contained in the smoke itself. From all these causes Dr. Arnott estimates a loss of seven-eighths of the whole heating-power, while Rumford estimated it as high as fourteen-fifteenths--each basing his conclusions on the kind of open fire-place chiefly in use in his own day. Unequal heating.—In a cold wintry day, when seated near a large fire, we may frequently hear persons complain of being scorched on one side and frozen on the other. This arises from the circumstance that, as most of the heat received from an open fire is radiated from the burning fuel, instead of being conducted by the air, this heat, diminishing in inten sity as the square of the distance increases, is very unequal, being too great at a small distance, and too weak at a greater ; while the draught, or current of cold air which feeds the fire with oxygen, acts like a chilling blast againet the aide of each person or object which is turned away from the fire. Strata of air unequally heated.—Lesides
the Inequality just alluded to, there la another, arising from this cir cumstance—that the entering current, being colder and specifically heavier than the air previously in the room, occupies the lowest stratum, and subjects the feet to a cold bath, which is frequently attended with bad consequences. Other objections are—the smoke and dust arialng from the use of open fires ; the toss of time attendant on the care which they demand ; the danger to property and to person which accrues from them ; the necessity (until lately supposed to be indispensable) of employing climting boys ; and many others.
Many contrivances have from time to time been brought forward to obviate one or other of those Inconveniences. Count Rumford sug gested the register-stove, the peculiarity of which consists In mar rowing the entrance or throat of the chimney by a plate which can be moved to vary the size of the aperture; by this means, particularly if the opening be near the fire, the very hot air directly from the fire enters before it can mix with much colder air from the room, and thus the draught is increased so as to lessen the chance of smoking. But - - the very circumstance which constitutes the excellence of this stove, namely, the rapid ascent of heated air up the chimney, illustrates the waste of the method generally by showing how much of the heating agent is lost. The almost interminable variety of open fire-places, both in the form of the grate Itself and in that of the opening in which it is placed, have been introduced either for an ornamental purpose or for the prevention of smoking ; the other evils enumerated are almost inseparable from the system.