Professor Bremer, of Yale College, states that 40 per cent. of moisture is needed to make air healthful. Now furnaces receive cold air containing little invisible moisture, and by heating: it a demand is created for much more. This is sucked up, as by a sponge, from walls and furniture, and especially from the lungs and capillaries of our bodies, thus causing dryness and sometimes inflammation of lips, nose, eyes, throat, and lungs. Experiments prove that while 40 per cent, of moisture is needed for health, furnace-heated air rarely has as much as 20 per cent., even when a few quarts of water are evaporated in the furnace chamber. Thus the inmates of the house breathe dryer air than is ever breathed in the hottest deserts of Sahara.

Thus, for want of proper instruction, most American housekeepers who use stoves and furnaces not only poison their families with carbonic acid and carbonic oxide, and starve them for want of oxygen, but also diminish health and comfort for want of a due supply of moisture in the air. And often when a remedy is sought, by evaporating water in the furnace, or on the stove, it is without knowing that the amount evaporated depends, not on the quantity of water in the vessel, but on the extent of evaporating surface exposed to the air. A quart of water in a wide shallow pan will give more moisture than two gallons with a small surface exposed to heat.

There is also no little wise economy in keeping a proper supply of moisture in the air. For it is found that the body radiates its heat less in moist than in dry air, so that a person feels as warm at a lower temperature when the air has a proper supply of moisture, as in a much higher temperature of dry air. Of course, less fuel is needed to warm a house when water is evaporated in stove and furnace-heated rooms. It is said by those who have experimented, that the saving in fuel is twenty per cent. when the air is duly supplied with moisture.

There are other difficulties connected with furnaces which should be considered.

The human body is constantly radiating its heat to walls, floors, and cooler bodies around. At the same time, a thermometer is affected in the same way, radiating its heat to cooler bodies around, so that it always marks a lower degree of heat than actually exists in the warm air around it. Owing to these facts, the injected air of a furnace is always warmer than is good for the lungs, and much warmer than is ever needed in rooms warmed by radiation from fires or heated surfaces. The cooler the air we inspire, the more oxygen is received, the faster the blood circulates, and the greater is the vigor imparted to brain, nerves, and muscles.

Every woman ought to know all the dangers connected with furnaces and how to remedy them. The following may aid in this duty:

When a furnace does not draw well, it often is owing to the stoppage by fine ashes or soot, and then the smoke-flues must be cleaned. The fewer and more simple the smoke-flues the less this trouble will occur. Sometimes the shaking of a furnace makes cracks in joints, and this causes outflow of gas and also diminishes the draught.

When iron is very hot, it burns the particles floating in the air, making an unpleasant smell and dryness. A large furnace, therefore, is better than a small one that must be kept very hot.

Water should be evaporated in large surfaces, and so as to deposit dew on windows.

Heated air passes off by the shortest courses, and it is often the case that the more distant rooms thus warmed have no ventilation and little renewal from the furnace air, and this is often shown by a fetid smell.

Furnaces where air is heated in the furnace-chamber by coils of steam or by hot water, though costing more at first, require much less fuel, and do not involve the evils of warming by hot iron.

The safest and pleasantest way of warming a dwelling is by steam-coils, provided there are fire-places or hot-air flues to carry off bad air. Without these, this is the most un-healthful mode of all, as there is no fresh air brought in, and what is heated is breathed over and over, till it is poisonous.

The want of care in regulating the dampers of the air-box often makes a house cold, however great the furnace lire. A strong wind requires the dampers nearly closed, especially when it is on the side where the air enters from without. Every furnace should be supplied, not by cellar air, but by air taken through a shaft from a height, and so more pure.

Remember that an open fire, or an opening into a hot-air flue, will ventilate properly in all seasons and all weathers. The opening should be at both the top and bottom of the room.