Candle Power

This question and its answer have been until recently of interest to scientists only. But since one rnethod of lighting is coinpeting with the other for superiority the question of lighting power has seenringly becorne a public matter. How many oandle power? The question is very simple and yet mysterieus to the layman. For measuring the lighting power the most reliable results are obtained by meaiïs of a grease spot. In its most simple application the experiment can be tried easily at home. A sheet of white paper with a grease spot in the center is put into a frame and placed between two flames of different lighting power - for instance, between an ordinary candle and a lamp. When the frame is equally distant from the two unequally bright flames, the grease spot can be seen plainly on both sides. By moving the frame with the sheet of paper slowly toward the less brilliant light - that is, the candle - it will arrive finally at a point where the grease spot has apparently disappeared on both sides of the paper. This deception must always occur when on both sides of the paper an equal brightness prevails and no side light exists. Having reached this point, it can be ascertained how mtich stronger is the light of the lamp than that of the candle. If the candle is 20 inches distant from the paper and the lamp 60 inches and yet the brightness on both sides of the paper is the same, then the light of the lamp will be as strong as that of nine candles. The calculation is based upon the distances, the figures of which are multiplied by themseJves and then divided - here, , f or jnstance, 60 times 60 divided by 20 multiplied by S-ö equals 9. This, of course, is the most primitive method for measuring light, but it ia the principie for all the delicate