The industrious bees, then, are an example to mankind. If people dwell in close rooms, they must cause an artificial breeze of fresh air to blow through them. Having shut out the great wind, that it may not chill too much by its uncontrollable currents, they must introduce such a little wind as they can keep thoroughly under control, but which nevertheless is sufficient to perform the office of purification as far as it is required. This process of causing an artificial wind to blow through the inside of a dwelling is called _ventilation_, from a Latin word which signifies “to blow” or fan with the wind. In very hot climates where dwellings need to be ventilated for the sake of coolness, as well as for purification, men follow precisely the example set by the bees. They hang up broad and stiff canvas fans, which they call _punkas_, near the ceiling, and cause these to flap backwards and forwards constantly, by pulling them to and fro with ropes. In more temperate climates, it is rarely found necessary to take all this trouble, for the air readily makes currents of its own accord inside of rooms, if only allowed to do so. All that is necessary is the furnishing of a free passage into the room, and a free passage out, and it will then make a clear march through. One opening will not do, when fans are not kept going, because then the entering and departing air would meet face to face and obstruct each other. There must be “in” and “out” doors, just as one sees in much frequented offices and banks, in great towns. A very effectual plan for securing the ventilation of a dwelling room consists in carrying a pipe of perforated zinc across the house, from outside wall to outside wall, just beneath the ceiling, allowing the ends to pass through the walls quite into the open air; then whichever end of the pipe chances to be most towards the quarter of the heavens from which the wind is blowing, should be closed with a plug, a free passage being left for the escape of the heated air through the opposite end. A number of holes should also be made through the door, near its bottom, until altogether they afford as much room to passing air as the inside bore of the zinc pipe. If you cannot manage to fix such a zinc pipe across the ceiling, why take out one or two of the panes of the window, and put into their place, plates of what is called _perforated zinc_ (zinc plates pierced full of holes), such as you may buy for a trifle at any ironmongers. That is the next best thing you can do.