This is the reason why drafts are experienced from the crevices of doors and windows : the heated and respired air passes off by the ventilator; to make up for what so passes oit fresh air flows into the bottom of the building, and as, when the weather is cold enough to make us abut the doors and windows, in gress by a duct equal to that of egress is prevented, to make up, by the rate at which it enters, for the difference in the sixes of the apertures of admission and emission, the air that finds its way in through cracks and crevices, enters with so at a velocity as to cause the chilling currents we experience.
Instead of suffering ventilation to take place at the pleasure of the air, I re strict and regulate it thus :—I first have the window. of the place nailed down, to prevent them from being ever opened ; I then have the joints and crevices, both of these windows and of the room in general, so filled with putty, or so treated with any kind of lute or luting, that will answer the purpose, as shall pre vent their becoming channels through which drafts or currents way find their way either into or out of the place. I then have the doorways arranged thus:— Removing the present doors, the door way is made six feet wide, by about the same height, and into it is fitted a cylinder (of wood or metal) closed at both ends, end placed upright on one of them, so as to appear somewhat like a cask built into the wall. Through the side of this cylinder I have two apertures cut, each about four feet wide, by the height of the cylinder inside its ends ; which apertures are opposite, the middle of each being in the lino of the centre of the cylinder, so as to leave a way of about four feet wide, right through the middle of it into the place, es, shown above, where the cylinder is represented placed in the wall, with the apertures in it. In the moire of the cylinder, there is now put (perpendicularly) a shaft, of about three inches diameter and of the length of the cylinder ; and having it, and the centres of the to and bottom of the cylinder, so prepared and fitted to each other, that the shaft may easily turn round, or revolve - then there are fixed on it, at right angles to each ether, eight arms or radii, four at top, and four at bottom ; the bottom four being exactly under the upper ones. To these arms there are fixed four sheets, or pieces of iron plate, Of such lengths and widths as will just go into, and fill up, (though without touching,) the space left between the shaft and the aide of the cylinder; and these things being so done, that the plates or leaves fixed on the arms may turn easily round, inside the cylinder; and the ends and sides of these leaves being so fitted to each other that, when the leaves are turned round, there may not be a space greater than about the sixteenth of an inch left be tween them, the arrangements fbr the door-way are complete; and the cylinder through which the place is entered, hes within it four leaves or wings, some what like the fans of a winnowing-machine. fixed perpendicularly.
Now, the abet of these arrangements is this :—Were a common door to be made use of, whenever it was opened, flnieingress or egress would be given to air, and it would pass from, or mto the place, as circumstances dictated. But with a door arranged in this way, no air can at any time pass either into or out of the plain, excepting by the narrow specs or envies left between the edges of the leaves and the inside of the cylinder; since, the leaves being all at right angles with each other, and the ,two apertures in the cylinder being neither of them so wide as to be equal to ninety degrees of a obeli, of the same diameter as this door-way cylinder, it fbllows that, turn, or cause the leaves to revolve in what way we may, two of them will always be within the uncut parts of the cylinder, and constantly interposed between the inside of the place and the open air; and in oonsequence, there never can be any other passage for air into, or out of the place, by this door-way, than by the space or crevice between the edges of the leaves, and the inside d the cylinder.
When the windows and door are thuslinished, I primed as follows with the ventilator :—To the aperture in the wiling. through which ventilation takes place, there is fixed a pipe of an equal diameter with that aperture; which pipe goes through the roof and then descends, and opens into a reservoir or cistern, situated on the outside of the building. Now, with things thus arranged, and with the cistern so fax lifted with water that the end of the ventilation-pipe is immersed a few Inches in the water, the machinery by which the warm air n in jected is set to work, when sir, flush, andof a temperature plowman° the feelings, is injected into the bottom of the building, at a rate sufficient Air the consumr tion of the people inside. The pipes which convey,this air, arose contrived and arranged, as to distribute it ever the whole surfaee of the floor, in a way which renders its introduction imperceptible; and consequently inconvenience fivm drafts or currents of it is guarded against. As fast as it is distributed over the floor, it gives place to the air that follows it, and rises towards the ventilator. In its ascent it passes the persons of the people in the place ; and becoming, from the heat imparted to it by their bodies, and from the deteriorating effects of their respiration, lighter, it rises more rapidly towards the ventilator.