PHYSICS. 129 



stance capable of disappearing in some way as the carbons 

 burn, the substance used by the discoverer being either kao- 

 lin or a mixture of sand and powdered glass. To prevent 

 the more rapid consumption of the positive carbon, it is 

 made of proportionately greater cross section, the author 

 having found that the relative rapidity of consumption de- 

 pends on the strength of the current. The light is double 

 that given by a regulator, and with an ordinary Gramme 

 machine current four lights were produced at the same 

 time. 



Experiments have been made in both London and Paris 

 with the electric candle of Jablochkoff, using two carbon 

 strips placed side by side, insulated from each other by some 

 non-conducting substance which melts or volatilizes as the 

 carbons burn. At the West India Docks in London four of 

 these candles were simultaneously burned with the current 

 from one magneto- electric machine. The large yard was 

 brilliantly illuminated, although the candles were enclosed in 

 ground-glass shades ; so that it was possible to read small 

 print at a considerable distance, while at the same time the 

 eyes were not affected by the glare, as is the case with the 

 ordinary electric light. The second trial was the lighting of 

 the top story of one of the large warehouses, and the third 

 the lighting-up of a large vessel at the quay, both of which 

 were successful. Each candle gave a light equal to that 

 from 100 gas-lights, and at a very much less cost. 



Another form of Jablochkoff's light has been variously 

 tried, which seems likely to be of more practical use than 

 the candle. It consists of a thin kaolin plate, only four mil- 

 limeters thick, but eisjht centimeters lono^ and two or three 

 wide, having the conductiiiGf wires fastened in orooves at 

 the ends. These wires are coarse, and come from the sec- 

 ondary coil of an inductorium, the primary coil being in the 

 circuit of an Alliance magneto-electric machine, driven by a 

 three-horse engine. When the secondary current crosses 

 the kaolin plate it apparently ignites, giving a soft mellow 

 light equal to that from eight gas-burners. In the Paris ex- 

 periments three electric candles, each equal to five kaolin 

 lights, were operated in the main circuit, while ten of the 

 kaolin lights were operated by as many secondary circuits, 

 thus making it possible to feed twenty-five lights at once in 



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