VENTILATION. The act of renovating the air of chambers, houses, ships, and all kinds of buildings or places. We may exist ibr several days without food, but we die, if deprived only for a few minutes of air. As air is necessary to life, so is pure air to health. But it appears that this important fact escapes the attention of the greater part of mankind, who are prone to blame the cook or the purveyor for the greater part of their ailments, without reflecting upon the impure air they may have been inspiring at the rate of about two gallons per minute. The oxygen gas, or vital portion of the atmosphere that enters the lungs, is changed at each respiration into carbonic acid gas. This gas, as is well known, it if inspired alone, or even if a large proportion of it be mixed with the atmospheric air. But by an admirable proviston of the great Author of Nature, this contaminated air is renderedspecifically lighter than the pure atmosphere, from the heat it has derived from the lungs, and consequently rises above our heads, during the short pause between our respirations •, thus in suring to us always a pure draught of air, unless we prevent it by artificial means.
It is not, however, always owing to a deficiency of oxygen, that the air of rooms or crowded places becomes pernicious to health. A council of health, estaidished by the French government, proved that in an atmosphere which had not lost one-twentieth part of its oxygen, an animal miasmata was diffused in vapours; that by suspending, in such atmospheres, a glass vessel filled with ice, the vapour diffitsed in the air becomes condensed bn its surface, and the liquid thus obtained by condensation, being collected in another vessel suspended underneath the former, exhales a fetid odour, and speedily undergoes the putrid fermentation, when exposed to a temperature of 79' Fahr.
Certain gaseous and other vapours may be mixed with the air we breathe, without producing any very marked inconvenience ; but the effeuts of a mixture of many other kinds are highly dangerous, and more quick in their action than even those of animal miasmata. A constant renewal of the air is absolutely necessary for its purity ; for in all situations, it is suffering either by its vital part being absorbed, or by impure vapours being disengaged apd dispersed through it. Ventilation therefore resolves itself into the securing a constant
supply of fresh air. Rooms cannot be well ventilated, that have no outlet for the fur, and this, from the superior levity of foul air, should be made at the highest point that can be obtained, and so arranged m to diffuse the fresh air that enters over the upper part of the room, and not inconvenience the in the room, by descending upon them in a current. There should be a AT:17y to every ISOM, which on no account should be stopped up with a chimney board, mils often the case in bed-rooms. We have observed also, in many houses, that the top sashes of windows of the upper rooms are made fast; now if these were made to slide downward, instead of the lower sashes upward, increased salubrity, as well as security, (especially in the case of children,) would be obtained. In whatever way fresh air may be made to enter an apartment, it should be, as far as may be practicable,at the part remotest from the fire-place, in order that it may traverse the whole apartment in its passage to the chimney. The most effective species of ventilation is that in which nature is adopted as the guide. The simple action of the sun, no less than the devastating phenomenon of the African tornado, tend to the same result. We have only to change the temperature of the air which surrounds us, and a new portion will rush in from the adjacent and purer parts, to supply its place. From this it is obvious, that a lamp placed in an aperture of the ceiling, in any large and crowded room, will tend to purify the air. This is precisely the case in our large theatres, as that at Covent Garden, where the great glass chandelier, with its numerous gas burners, gives out a great quantity of heat, immediately under a large funnel, which passes through the roof, into the open air. The rarified air which thus rushes through the funnel, is constantly succeeded by continuous fresh currents, entering at numerous apertures beneath, to restore the equilibrium of pressure.