Page:Popular Science Monthly Volume 30.djvu/251

Rh that travels nearly 200,000 miles in a second. By convection, or hot air from iron surfaces, we have a comparatively dead or dormant heat that moves only a few feet in the same time. By radiation from open fires the air is the coolest thing in the room; by the air-heating method it is the hottest. By open fires the lungs get less heat than any other part of us, and so are braced and strengthened; by the hot-air process they get more heat than any other part, because the hottest air rises uppermost about the head, and so is inhaled, making the lungs tender and sensitive to cold on our going out. Put a thermometer at the floor, and another at the ceiling, in a room heated by the hot-air process, and you will find the air at the ceiling from 15° to 45° warmer than at the floor. And so the head is surrounded by a torrid atmosphere, while the feet may be cold.

We want to warm our bodies, not the air. Cool air is denser, contains more oxygen, and warms the blood more than hot air, besides refreshing and strengthening the lungs, and bracing them against injury on going out. We want air with a normal amount of ozone. We get it with the ozone all destroyed by the hot-iron surfaces. The Professor of Chemistry in the London University (Dr. Graham, a very high authority) says ozone is destroyed at 140°.

Suppose the top of your house removed, and the sun shining freely down into it in winter. Your floor, walls, furniture, and your clothing, will have a temperature of, say, 100°, while the air itself will be only at 50° or 60°. An open fire is a miniature sun, and its radiation is governed by the same laws as that of its great prototype. With an open fire put in proper position in your room, while your walls and floor will be at about 80° or 90°, the air will be at 50°. Replace this open fire by an air-heating arrangement, and your floor and walls will be found to be only 50°, more or less, while the air rises from your close stove or your hot-air register at from 140° to 250°. If you doubt it, put a thermometer in your register, and see.

What do we want of such air as this? Evidently nothing, and so kind Nature sends it upward as quickly as possible, to get it beyond our reach; but we defeat her beneficent intent by closing the ventilators at the ceiling; and so after cooling somewhat it descends, still far too warm (and robbed of all its ozone, and the refreshing qualities of natural air), to enfeeble the lungs, and render them susceptible of injury on going into the external air.

The only remedy for all these mischievous conditions and effects is entirely to abandon the plan of applying the heat to the air—of making the air the carrier of heat. Heat wants no carrier, any more than light. It can outfly Mercury "and the swift-winged couriers of the air." Put your fire in proper position; take away the iron and brick casings that inclose it and obstruct its natural movements, and, quicker than you can think, the heat will be flashed all over your room; darting out in straight lines in every direction from the surface of the