therefore rises and at first collects in the upper part of the room, unless it is allowed to escape.
In a room that has a fire-place a stream of air is usually passing up the chimney, fresh air coming in by the cracks round the doors and windows. No bed-room should be slept in without a fire-place unless ventilation is otherwise provided for; even the quan-tity of air coming in round the window and door is not sufficient, it is therefore much better to sleep with the window open. This may be done without causing a draught, by placing a board three inches wide on its edge under the lower sash, which is thus raised, caus-ing a space between the two sashes in the centre of the window; through this the air enters and being directed upwards does not cause a draught.
90. It is much more desirable to let the air come into a bedroom through the window than through the door, as the house being closed at night the air often comes through the drains or damp cellars, and is not as pure as that which comes from outside the house. Gas is not desirable in close sitting or bedrooms, its effect on the air being much more injurious than candles or lamps.