NATURAL PHILOSOPHY. 105 



solar light. Perhaps one of the most striking displays of the charac- 

 ter of the electric light followed. The electrodes were immersed in a 

 globe of water, and still the light continued gleaming forth in all its 

 brilliancy. Those who are familiar with the oxyhydrogen light, and 

 the peculiarly white and somewhat intense light of the camphine 

 lamp, might have felt doubtful of the result of a contrast with these ; 

 but the "electric effulgence outshone both to a remarkable degree. It 

 was stated at the time, that a volume of light equal to that of ^ 10,000 

 wax candles could be evolved by the apparatus from a square inch of 

 actual illuminating surface. It was said that a light of from one 

 candle to 100,000 might be obtained, and sustained, by this new 

 system ; and with regard to the cost of production, the light equal to 

 100 wax candles was obtainable at the rate of a penny an hour, or 

 about, as it is stated by the inventor, one twelfth part of the cost of 

 gas for the same period, and producing the same degree of illumina- 

 tion. 



The character of the electric light presents several remarkably in- 

 teresting features, most of which belong to no other artificial light 

 whatever, and assimilate it to that of the sun itself. The heat evolved 

 is vastly disproportionate to the light produced, as may be conceived 

 from the fact, that the lamp, when pouring forth a volume of light 

 equal to 800 candles, did not emit more heat than that of one Argand 

 lamp equal to six or seven candles. The light has been displayed, 

 not only in air and under water, but also in alcohol, ether, sulphuret 

 of carbon, and in atmospheres of carbonic acid, nitrogen, and hydro- 

 gen. The apparatus constructed, for domestic use gives a light equal 

 to from eight to forty candles. 



There is another point which appears to be important in consider- 

 ing the applicability of this beautiful light to the illumination of 

 streets or great areas, and that is its diffusibiiity. The ordinary modes 

 of illumination are incapable of giving luminosity to the solid and 

 aqueous particles in the atmosphere for any considerable extent, but 

 the electric light effects this admirably, for even if a person places 

 himself in the shadow under a wall, he can easily see to read ; so 

 that the argument brought up by some, that, in attempting to light 

 large spaces with a single light, much of the area must be thrown in- 

 to the shade, is of no weight. 



But there is one chemical peculiarity about this light which de- 

 mands a brief notice. It is found to possess those chemical powers 

 of decomposition, which have been regarded as peculiar properties of 

 the solar light, and which are known under the name of actinism. 

 Preparations of silver, which turn black when exposed to the sun's 

 light, blacken also before the electric light ; and the chemical union 

 of mixed gases, hydrogen and chlorine, has been effected by placing a 

 jar containing them hi the light of the electric lamp. 



APPARATUS TO PRESERVE THE ELECTRIC LIGHT CONSTANT. 



Ax the sitting of the Paris Academy of Sciences on the 15th of Jan- 

 uary, M. L. Foucault reminded the Academy that five years ago 



