Great precautions should also be followed in the treatment of certain articles of furniture, such as beds and mattresses, which must be renovated or replaced, and which should never on any account be used until thoroughly dried. Sanitary treatment, such as adopted for houses, should be applied with no less vigilance to stables and barns. One peculiar feature it is important to note, though it can only be accidentally produced: it is the possible alteration of the water of wells and springs of potable water, in whose neighbourhood matter in a state of decomposition may have been deposited, or piles of excrementitious and organic debris, or sources of water supply which may have been contaminated by the contents of privy vaults. Attention should be directed to this danger. To disinfect cellars into which, by agency of the inundations, the contents of privy vaults may have penetrated, commercial zinc sulphate may be used, either by sprinkling it in powder in the cellar, or by watering the ground when the water has gone down with a concentrated solution of this salt. Concentrated solution of iron sulphate does well, but the disinfection is not so complete as with salts of zinc; it is, however, cheaper. =Ventilation.=--The objects of ventilation are twofold--first to get rid of the poisonous gas (carbonic acid) exhaled from our lungs, and second to furnish a supply of life-supporting gas (oxygen, as it exists in fresh air) to our lungs. For healthy living, every adult individual requires at least 1000 cub. ft. of space, or a room 10 ft. square and 10 ft. high; into this room should pass 3000 cub. ft. of air every hour. In dwelling-rooms, and especially in bedrooms, the fireplace should always be left unclosed, and the flue or damper open for ventilation. The windows should pull down from the top, and a piece of wire gauze should be fixed along the open space at the top; or a pane of glass should be perforated with holes capable of being closed in stormy weather. All rooms, and especially sleeping apartments, should be well aired during the day. A good and simple test for impure air is to take a clear glass bottle with a glass stopper, holding about 10 oz., and wipe it carefully inside and out. On entering a room, the air of which you wish to test, stuff a linen cloth into the bottle and rapidly withdraw it, so as to allow the air of the room to enter the bottle. Then carefully place a tablespoonful of clear lime water in the bottle, and replace the stopper. Shake it for a few minutes; then, if the air is pure, the lime water will remain clear. If bad, and loaded with carbonic acid, the lime water will become turbid, or even milky. This is because lime and carbonic acid together form chalk, which gives the milky appearance. It must be remembered that this test has no reference to the ammonia which often exists abnormally in the bad air of towns, nor does it indicate the presence of disease germs or poisons due to paint, wall-paper, &c.