Iviii PROCEEDINGS. 



those in the less unsteadj' but inoie expensive illumination of the " fin de siecle 

 age. 



In the tallow dip we have a crude retort, producing hydrogen which while 

 burning raises to a white heat, the minute particles of carbon set free in the action 

 •of combustion, and by far the greater part of the potential energy present is wasted 

 in producing carbonic acid and water or in the form of heat waves, leaving but a 

 small portion of energy to be converted into light waves. The same action of 

 ■course takes place in the oil or gas light, the advantage in the latter, from an 

 •economic point of view being the production of the carbon-charged Hydrogen at 

 a central point (the gas house) where a given amount of gas can be produced 

 under much better conditions than can be obtained in the numerous and tiny 

 individual gas retorts of the candle or oil lamp. 



In an electric light whether arc or incandescent, the principle remains the same 

 and it is not the electric current we see but highly heated carbon, and the energy 

 necessary to heat the carbon points or filament to the proper illuminating point is 

 obtained from the coal under the boilers of the electric light station through the 

 medium of the rapidly revolving wires in the dynamo cutting the unseen but all 

 powerful lines of force of the magnetic field, and not from a direct chemical 

 process as in the other examples of light. 



Now the modern dynamo, as a machine for the conversion of mechanical into 

 electrical energy, is a most efficient apparatus, and usually returns in the form of 

 electricity, 90 to 95 per cent, of the mechanical energy put into it, a result we 

 may well be proud of when it is considered that with the most efiicient steam 

 plant not more than 5 per cent, of the energy possessed by the burning coal is con- 

 verted into mechanical energy in the engine ; and as regards the systems of distri- 

 tribution, the loss is not, or need not be, more than 5 to 10 per cent, in 

 transmitting the electrical energy to the points of conversion. 



And so we find that here at the point of conversion into light (or the lamps) the 

 greater part of the waste takes place ; and as there is not the same chemical action 

 in this light as in the oil or gas flame, we do not find this waste in the form of 

 carbonic acid or water, but almost wholly in heat waves or invisible and therefore 

 useless radiation. Now so long as we iitilize carbon as the source from which to 

 obtain light so long will we have this waste of energy in heat, as heat alone, 

 whether it be furnished by the gas flame or electricity', will produce (in carbon) 

 the necessary molecular action resulting in light waves. So it seems probable 

 that we shall employ other processes and proceed on new lines before any great 

 advance can be made in illumination. 



In the light of the future, energy (probably electrical) will be converted into 

 luminous waves with a loss not exceeding, say, 5 to 10 per cent, in heat ; the light 

 will be practically cold ; and the power now required for one 16 c.p. lamp will give 

 us twenty. In looking for an example of a light of this character we naturally 

 think of the fire-fly and glow-worm, both of which may be said to be good 

 examples of a perfect light, at least as far as eflSciency goes. Careful tests have 

 been made on the light emitted by the fire-fly, and the results show that it is 

 practically heatless, less than 2 per cent, of the total radiation being in the form 

 of heat waves. It is true that the secret of its production has not yielded to our 

 tests, but we hope that, like many of nature's formuire, it will be solved, and the 



