62 THE POPULAR SCIENCE MONTHLY. 



These results are not only of obvious practical value, but they seem 

 to establish a fixed relation between current, temperature, and light 

 produced, which may serve as a means to determine temperatures ex- 

 ceeding the melting-point of platinum with greater accuracy than has 

 hitherto been possible by actinimetric methods in which the thickness 

 of the luminous atmosphere must necessarily exercise a disturbing in- 

 fluence. It is probably owing to this circumstance that the tempera- 

 ture of the electric arc as well as that of the solar photosphere has fre- 

 quently been greatly overestimated. 



The principal argument in favor of the electric light is furnished 

 by its immunity from products of combustion which not only heat the 

 lighted apartments, but substitute carbonic acid and deleterious sul- 

 phur compounds for the oxygen upon which respiration depends ; the 

 electric light is white instead of yellow, and thus enables us to see 

 pictures, furniture, and flowers as by daylight ; it supports growing 

 plants instead of poisoning them, and by its means we can carry on 

 photography and many other industries at night as well as during the 

 day. The objection frequently urged against the electric light, that 

 it depends upon the continuous motion of steam or gas engines, which 

 are liable to accidental stoppage, has been removed by the introduction 

 into practical use of the secondary battery ; this, although not embody- 

 ing a new conception, has lately been greatly improved in power and 

 constancy by Plante, Faure, Volckmar, Sellon, and others, and promises 

 to accomplish for electricity what the gas-holder has done for the sup- 

 ply of gas and the accumulator for hydraulic transmission of power. 



It can no longer be a matter of reasonable doubt, therefore, that 

 electric lighting will take its place as a public illuminant, and that, 

 even though its cost should be found greater than that of gas, it will 

 be preferred for the lighting of drawing-rooms and dining-rooms, thea- 

 tres and concert-rooms, museums, churches, warehouses, show-rooms, 

 printing establishments, and factories, and also the cabins and engine- 

 rooms of passenger-steamers. In the cheaper and more powerful form 

 of the arc-light, it has jn'oved itself superior to any other illuminant 

 for spreading artificial daylight over the large areas of harbors, rail- 

 way-stations, and the sites of public works. When placed within a 

 holophote the electric lamp has already become a powerful auxiliary 

 in effecting military operations both by sea and land. 



The electric light may be worked by natural sources of power such 

 as water-falls, the tidal wave, or the wind, and it is conceivable that 

 these may be utilized at considerable distances by means of metallic 

 conductors. Some five years ago I called attention to the vastness of 

 those sources of energy, and the facility offered by electrical conduc- 

 tion in rendering them available for lighting and power-supply, while 

 Sir William Thomson made this important matter the subject of his 

 admirable address to Section A last year at York, and dealt with it in 

 an exhaustive manner. 



