that happen. Keep the bedstead, whatever else may go, to save the
sleeper from the carbonic acid on the floor.

How, then, shall we get rid of the foul air at the top of the
room? After all that has been written and tried on ventilation, I
know no simpler method than putting into the chimney one of
Arnott's ventilators, which may be bought and fixed for a few
shillings; always remembering that it must be. fixed into the
chimney as near the ceiling as possible. I can speak of these
ventilators from twenty-five years' experience. Living in a house
with low ceilings, liable to become overcharged with carbonic
acid, which produces sleepiness in the evening, I have found that
these ventilators keep the air fresh and pure; and I consider the
presence of one of these ventilators in a room more valuable than
three or four feet additional height of ceiling. I have found,
too, that their working proves how necessary they are, from this
simple fact: You would suppose that, as the ventilator opens
freely into the chimney, the smoke would be blown down through it
in high winds, and blacken the ceiling: but this is just what
does not happen. If the ventilator be at all properly poised, so
as to shut with a violent gust of wind, it will at all other
moments keep itself permanently open; proving thereby that there
is an up-draught of heated air continually escaping from the
ceiling up the chimney. Another very simple method of ventilation
is employed in those excellent cottages which Her Majesty has
built for her labourers round Windsor. Over each door a sheet of
perforated zinc, some eighteen inches square, is fixed; allowing
the foul air to escape into the passage; and in the ceiling of the
passage a similar sheet of zinc, allowing it to escape into the
roof. Fresh air, meanwhile, should be obtained from outside, by