Light is not the simple thing that it is considered to be by the general public. It is composed of many parts, qualities and manifestations. Its rays, when separated by the Spectrum, are seen to consist of "waves" or vibrations of differing degrees of rate and intensity. The lower range contains the heat rays, and it is interesting to know that there are rays of heat too far down in the scale to be evidenced by human senses that may be distinguished by delicate instruments. But there are rays still further down in the scale that are known to exist, theoretically, that cannot be registered even by the finest instruments. To gain an idea of the delicacy of these instruments, let us remember that Prof. Langley has an instrument called the "Bolometer," that is so delicate that it registers a change of temperature of one millionth of a degree, and will register the heat of a candle one and one-half miles distant from it. Light vibrations arise from combustion, friction, electricity etc., causing the Particles to assume increased Motion. Let us consider the report of the Spectrum. Beginning with waves or vibrations far below the sensibility of Man, the scale shows an advance until the first "warm" vibration of iron was reached. This first indication of warmth comes when the vibrations reach the rate of 35,000,000,000,000 _per second_. Then gradually they increase until a dull red glow is noticed--the lowest _visible_ light ray--when the vibrations are 450,000,000,000,000 per second. Then come the orange rays, then the golden yellow, then the pure yellow, then the greenish yellow, then the pure green, then the greenish blue, then the ocean blue, then the cyanic blue, then the indigo, then the violet--the latter evidencing when the vibrations reach the rate of 750,000,000,000,000 per second. Then come the Ultra-violet rays--invisible to human sight--but evidenced by chemical media. In this Ultra-violet region lies the X-Rays, etc., and also the "Actinic Rays," that produce photographs, sunburn one's face and blister the nose--that cause violent explosions in chemicals--that transform forms of Substance--that are employed to cure skin diseases, etc. These Actinic or Chemical Rays have an important role to play in plant-life, for they act upon the green leaves of the plant, causing a chemical change by which carbonic acid and water are transformed into sugar and starches. Some of the rays of the Ultra-violet region of Light penetrate substances formerly considered solid and impenetrable. And some of them emitted from Radium, etc., would destroy organic life if applied in sufficient quantities. Some of them are practically waves of Electricity so that Light and Electricity are seen to be closely related.