Evidences of Health Rays
The fact that these ravs are without heat may be demonstrated easily by merely standing’ behind .a window-glass on a clear cold winter day and noting the “warmth” of the rays of the .sun—the warmth that is generated upon absorption of the rays by the body-while the glass remains cold to the touch. The energy that brings a temperature of a hundred degrees or more in summer passes through many millions of miles of space in, which the temperature is far below zero. Think that fact over.
If the sun’s energy were merely con-vective or conductive heat the temperature of the space be¬tween the sun and the earth would be raised to the same point as that of the body producing the energy. The degree of heat created by the infra-red rays of sunlight depends upon the degree of opacity of their target, or the degree to which they are absorbed. When the rays reach any object, they either pass through it without change, are reflected (turned back), or absorbed to produce conversive or radiant heat. The nearer to perfect black the object they strike is, the greater the absorption. If the bulb of a thermometer is coated with lampblack these rays Mali be absorbed to such an extent that the thermometer will record a much higher temperature than it will under the same conditions without the coating, and a temperature elevation will he recorded even when the sunlight reaches the bulb through a thin layer of clear ice.