But perhaps the simplest way is to have ample openings (from eight to twelve inches square) at the top and bottom of each room, opening into the chimney-flue: then, even if a stove is used, the flue can be kept heated by the extension of the stove-pipe some distance up within the chimney, and the ascending current of hot air will draw the foul air from the room into the flue.

This, as before stated, must be completed by a fresh-air opening into the room on another side: if no other can be had, the top of the window may be lowered a little.

The stove-pipe _extension_ within the chimney would better be of cast-iron, as more durable than the sheet-iron.

When no fire is used in the sleeping-rooms, the chimney-flue must be heated by pipes from the kitchen or other fires; and, with the provision for _fresh_ air never forgotten, this simple device will invariably secure pure and well-oxygenated air for breathing.

"Fussy and expensive," may be the comment; but the expense is less than the average yearly doctor's bill, and the fussiness nothing that your own hands must engage in.