shop and stayed there for a number of years. After 

 patenting a novel kind of electromagnet, he turned 

 to the electrical lamp, and the innovations he in- 

 troduced gave a tremendous impetus to the com- 

 mercial application and exploitation of the dynamo. 



Jablochkoff found a means of producing a carbon 

 arc that regulated itself without the use of any 

 mechanism. 1°^ He based his lamp (called a "candle") 

 on the circumstances that if two carbons are placed 

 side by side and parallel to one another, and so close 

 that an arc could form at the ends, it would continue 

 to burn until the carbons were entirely consumed. 

 An insulating material — first kaolin and then a 

 mixture of barium and calcium sulphates — was used 

 to separate the two electrodes. The role of the spacer, 

 called a "colombin," is not clear; apparently it 

 provided some of the glow, and perhaps it reduced 

 the voltage necessary to maintain the arc. Direct 

 current was first tried, but since the positive electrode 

 in an arc burns twice as fast as the negative, alternatmg 

 current was used to make both burn at an equal rate. 

 Each "candle" provided a light equal to that from 

 200 to 500 standard candles, depending on the 

 generator and the particular circuit (fig. 80). 



With this device, Jablochkoff solved two of the 

 problems of the subdivision of the electric light — 

 that of placing several lights in the same circuit and 

 that of reducing the intensity of the arc light. Al- 

 though the "candles" flickered somewhat and only 

 lasted for one or two hours, the light was whiter and 

 brighter than that from gas, and it was not as blinding 

 as that from the ordinary arc light. As used in an 

 onyx globe (fig. 81), it gave a broad and diffused glow 

 that seemed to have been occasionally on the pinkish 

 side. Since there was no mechanism to be con- 

 stantly fluctuating in the circuit and causing unstable 

 operation of the other lamps, several "candles" could 

 be placed in a single circuit. To further increase the 

 subdivisibility of a circuit of electric "candles," 

 Jablochkoff first tried to use condensers and then 



'»» French patent 112024 (filed March 23, 1876; additions, 

 September 16, October 2, October 23, November 21, 1876, 

 March 31, 1877, March 11, 1879); British patent 3552 (Sep- 

 tember 11, 1876); L. Denayrouze, "Sur une Nouvelle Lampe 

 electrique imaginee par M. Jablochkoff," Comptes rendus, 

 1876, vol. 83, pp. 813-814; Du Moncel, op. cit. (footnote 80), 

 vol. 5, pp. 472-475, 515-518; Engineering, 1878, vol. 26, pp. 

 125-127; William E. Langdon, "On a New Form of Electric 

 Light," Journal of the Society oj Telegraph Engineers, Xfill , vol. 

 6, pp. 303-319. 



T 



.^"v*u 



Figure 8o. — U.S. Patent Office model of the 

 Jablochkoff candle. {VSNM 252646, Smith- 

 sonian photo 8899-^.) 



PAPER 30: DEVELOPMENT OF ELECTRICAL TECHNOLOGY IN THE 19TH CENTURY: III 



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