For a house with fire-places of the usual construction, perhaps the simplest and most effective expedient is to admit the fresh air into the entrance-hall, and there warm it by means of a low-temperature stove or by hot-water pipes: its passage into the several. rooms can then be provided for by regular channels, behind the skirting or other wise. In America perforations are frequently made in certain parts of the doors, before which silk curtains are disposed, so as to temper the currents. It is almost unaccountable that in this country the plan of warming the lobby and staircase is seldom resorted to. To say nothing of the comfort thus diffused through the 'whole house, and the benefit in point of health, especially to weakly constitutions, the econ omy of the arrangement is beyond dispute. In the sitting-rooms, not more than one half the usual quantity of fuel requires to be burned in the open fires; and in the bed rooms, as a rule, fires arc rendered altogether unnecessary in the coldest weather. It ought to be observed that when air is admitted by a regular and free channel, compara tively little is strained in by the windows and other byways.
f'entilatian by Fans and fan-wheel has been for many years used in. factories, to which it is particularly applicable, from the readiness with which it can be kept in motion by the engiue. It is essentially the same as the barn-fanuers; the air is drawn in at the center of the wheel, and flies off at the circumference by centrif neal force. The fan is placed at the top of a flue, into which branches from all parts• of the establishment proceed; and when it is set in motion, it draws off the air from every apartment communicatine with it. Dr. Arnott observed that in the fan-wheel as well as in the air-pump or bellows invented by Dr. Hales, a great deal of power was wasted by " wire-drawing" the air—that is. making it squirt through small valves or other narrow openings. To obviate this, he invented a ventilating-pump, which sup plied a hospital with fresh air, requiring no other motive power than the descent of the water used in the establishment from a high reservoir to the lower parts of the building. It is described in his work on Warming and Ventilation.
Transference of )teat from the used air to is the kind of economy which is put in practice in the respirator (q.v.) and in the caloric engine (q.v.). What ever difficulties—or impossibilities, as some maintain—there may be in the way of turning this transferred beat into a fresh source of power, nothing seems simpler, in theory at least, than to economize heat in this manner for the warming of dwellings and similar purposes. The idea originated with Dr. Arnott, many years ago, who that', illustrates it in the case of water: Suppose a vessel of boiling water, with a thin metallic tube issuing from the bottom, and having a stop-cock at its extremity; and a similar vessel of water at freezing, the tube of which is larger, and envelopes the other.W . hen both are flowing simultaneously, the hot water, if the tube is long enough, will have lost all its excess of heat before getting to the end of the tube, while the counter-current will have gained all that the other lost. In an experiment with tubes 6 ft. long, the boiling water from the first vessel issued from the pipe at 34°, and the freezing water from the second vessel issued from the pipe at 210°. It is clear that if the first vessel were a bath, the warm water in it, after being used, might in flowing out he made to heat the cold water front a reservoir, flowing into another bath below. We are not i aware that the principle has ever been acted upon; but the possible economy of heat s obvious, and it only requires mechanical ingenuity to realize it.
It will at once strike the reader how desirable it would be to do the same with the impure heated air which we are obliged to eject from our dwellings. Where the ventila tioni a tion depends upon the draught of a common chimney, it would seem impossible to bring the entering air in contact with that which is escaping; but where the mechanical force of a pump or a fan is employed, nothing seems simpler than to make the two cursento rnn counter to one another for a certain distance in close contact through a system of tubes. The smoke even, which, with the most economical arrangements, still issues
from the flues at a temperature considerably above that of the building, might be drawn into the current along with the foul air of the apartments, and the whole reduced nearly to the temperature of the atmosphere before being allowed to escape. Of course there must be loss in the transference; but a large percentage would be saved, and the con sumption of fuel would be reduced by that amount. Were this " double-eurrent ventilation" applied to churches, ball-rooms, theaters, etc., where thousands of persons are assembled, Dr. Aruott believed that "no other heating apparatus would be required but the lungs of the company." Notwithstanding all the improvements recently effected, it is beyond doubt that this important branch of the art of living is still in a very rude and imperfect condition. A writer in the Quarterly Review for April, 1866, in a very suggestive article on Coal and Smoke, points to the radical error of the existing system, when he remarks that " in a household fire heat is, as it were, manufactured on a very small scale; and experience has proved that the cost of productionof an article has always been inversely proportionate to the scale of its manufacture." He accordingly suggests that " it seems practicable, in a great measure, to supersede domestic fires, and to lay on heat (heated air), or the means of generating heat (low-priced gaseous fuel), to our houses pretty much as we now lay on gas." The abatement of the smoke nuisance, and systematic and thorough 'ventila tion, ought to be effected on a similar joint-plan, " by the chimneys of all b the houses with underground culverts, provided at intervals with high 'shafts, in which, if necessary, the draught upward might be increased by furnaces. We have long been familiar with extensive manufactories, covering large areas, in which are very numerous fires, all in communication with a single lofty chimney. With such an arrangement, no visible smoke should be produced, and with due attention a smoky chimney should be impossible." In the case of existing houses, the amount of reconstruction necessary might be a serious obstacle; but in building a new street it might easily be made to empty its entire smoke through the medium of a single tall tower resembling those meditoval campanili which are to be seen in Bologna and other Italian cities." It is further proposed to make the ordinary sewers serve the purpose of culverts for the passage of the smoke to the common chimney. The sulphurous acid of the smoke would destroy the noxious qualities of the sewage gases, and improve the sewage for agricultural pur poses; and instead of foul gases escaping through every or leak in the sewers, as at present, the powerful suction of the ventilating shafts would draw in fresh air, thus establishing a thorough system of atmospheric sewage. Another effect of the common chimney system would be to make the transference of heat, or double-current ventila tion, spoken of above, easily practicable in domestic houses. The pipe through which the heated air and smoke were being drawn away might be made to give up its heat to the counter-current of fresh air which was being drawn in.
Even though such painstaking plans of economizino. heat might not pay at the present cost of fuel in this country, it is pleasing to think that there is such a resource in reserve. It is not with all countries as with us; and even our stores of coal are not inexhaustible. It is an unworthy and, in the real sense of the word, an inhuman maxim that bids us "let posterity look to itself." If the absorbing passion for present gain will not let us begin practising economy now, we may at least seek to devise and perfect plans to be in readiness when the necessity comes. It is not uncommon to hear the argument, that before the coals are done, something else will be discovered as a substitute. We are at a loss to imagine what the something is to be, unless it be the ingenuity to make the fuel that is now wasted in a year last a hundred; and this we believe to be quite possible.