Q. Why is there always a strong draught under the door, and through the crevice on each side?
A. The cold air rushes from the hall under the door, &c. into the room, to supply the void caused in the room (by the escape of warm air up the chimney, &c.)
Q. Why is there always a draught through the window crevices?
A. The external air (being colder than the air of the room we occupy) rushes through the window crevices to supply the deficiency, caused by the escape of air up the chimney, &c.
Q. Why is there more draught if you open the lower sash of a window, than if you open the UPPER sash?
A. If the lower sash be open, the cold external air will rush more freely into the room; but if the upper sash be open the heated air of the room will rush out; and (of course) there will be less draught.
Q. By which means is the room better ventilated, by opening the lower or the upper sash?
A. A room is better ventilated by opening the upper sash; because the hot vitiated air (which always ascends towards the ceiling) can better escape.
Q. By which means is a hot room more quickly cooled—By opening the upper or the lower sash?