Light Minus Heat

Almost froni the time that the vibra;ory theory of light was accepted scienific men have looked forward tothe day when it would be possible to produce ight without heat. For it is an unfor;unate fact that so far every effort to )roduce light has been accompanied by an enormous waste of energy due to the jroduction of useless heat. The siniplest way of producing light is by means of the combustión of soine compound of carbon. It does not matter whether the carbon is solid, as in a candle, or a fluid, as in a lamp, or in a gas, as in ordinary illuminating gas, the process is the same. The union of the carbon of the substance with the oxygen of the air produces the rapid vibration that the eye recognizes as light. Carbon, though the element usually employed, is notanecessary factor, for magnesium, potassium, iron - indeed almost any of the elements - will take its. place. Neither is oxygen a necessary part in the production of light. Chlorine will produce an even more brilliant light with certain substances. It is evident, therefore, that the rate of vibration and not the element employed is the principal factor in producing light. Unfortunately all methods of producing light by means of chemical combinations (such as the union of the carbon of the candle with the oxygen of the air) are accompanied by a very large production of heat waves, which in the majority of cases are utterly useless, if not absolutely troublesome. The old simile of a musician desiring to produce a certain high note being compelled to press down all the keys of bis instrument is an apt one. The lower notes are not merely useless, but they are positively annoying. Singularly enough, the first solution of the problem that was attempted successfully was by the aid of heat. A very small aniount of light waves are required for recognitton by the wonderfully developed special sense which man possesses. Itis intensity, not quantity, that is wanted, to use a technical term. Consequently if a very small partiële is heated to incandescence the light which it throws out bears a far greater ratio to the amount of heat required than itdoes if a large mass is simüarly heated. This is one' of the radical bases of the utility of the incandescent electric light. An extremely small filament is heated to incandescence through the resistance which it offers to the flow of an electric cnvrent. It gênerates heat, it is true, but the amount of heat thus produced is dircctly proportional to the mass of the carbon, which is very small. The light produced, however, is amply sufficient for all ordinary purposes. This solution, however, is highly unsatisfactory to scientists, however useful it is to the public at large. Light apart from heat altogether was wanted. The firefly, the phosphorescent sea animalcules and even the exhausted tubes of Geissler furnished the hope that there was yet some method of reaching the high note without pressing down the whole keyboard. Recently an extraordinary genius has appeared in this country who seems upon the verge of discovering, if not to have actually discovered, a method by which this might be done. Nikola Tesla, a man of independent fortune and most brüliant mind, who was for a time connected with Edison, has dared to experiment with rapidly alternating electric currents. The result has surprised the wildest dreams of the theorizers. He has succeeded in producing light of comparatively high intensity without the production of heat and apparently directly by the use of electricity. The halls of the Royal society of London and of the Franklin institute of Philadelphia have been illuminated by means of the light radiated froni bare copper wires in the open air carrying these so called Tesla currents. ' The wires were not hot. but they radiated from their surfaoe light and sent from one to another bands and streamers of the mysterious light which we see in the aurora borealis. The effect must be seen to be thoroughly appreciated, but when it is stated that the experimentar without difliculty succeeded in radiating light not only from an exhausted glass tube held in his hand, but also from his thumb, his nose and other features, the enthusiasm which swept over his audiences in London and in Philadelphia may be appreciated. As yet no useful application has been found for these wonderf ui new developments in electrical science, but they should be welcomed as a harbinger of further progresa.