THE CONQUEST OF NATURE 



other, or were, on the other hand, separated too widely; 

 and since there was a constant wearing away and 

 shortening of the points, and thus a constantly increas- 

 ing space between them, the great difficulty in making 

 a practical lamp lay in regulating this distance auto- 

 matically. It was finally accomplished, however, by 

 the invention of a Russian officer, M. Jablochkoff, in 

 1876. The " Jablochkoff candle, " as his lamp was called, 

 marked an epoch in the history of electric lighting. 

 One great merit of this invention was its simplicity, and 

 while it has long since gone out of use, having been 

 superseded by still simpler and better devices, it must 

 always be recalled as an important stepping-stone in the 

 progress of artificial illumination. 



The name "candle" for Jablochkoff 's lamp was sug- 

 gested by the fact that the two carbons were placed side 

 by side, instead of point to point, the light at the top 

 thus suggesting a candle. Between these two carbons, 

 and extending their whole length except at the very tips, 

 was an insulating material that the arc could not pierce, 

 but which burned away at a rate commensurate with 

 the shortening of the carbons. In this manner the points 

 were kept constantly at the proper distance without 

 regulating-machinery of any kind. This ingenious ap- 

 paratus had the additional advantage that it could be 

 placed on any kind of a bracket or chandelier that was 

 properly wired, thus dispensing with the cumbersome 

 frames and machines of the point-to-point carbon 

 arc lights then being introduced. 



One difficulty at first encountered in using the Jab- 

 lochkoff candle was the starting of the voltaic arc. In 



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