196 ELECTRIC LIGHTING. 



passable. A relative of True, the Paris lampmaker, at whose 

 house Kosloff's experiments were made, also worked at this 

 lamp with much enthusiasm without effecting any material 

 improvements ; and it was not until Konn had invented his 

 lamp in 1875 tnat ^ was possible to enter upon experiments 

 which held out any promise of practical advantages from 

 lamps of this kind. It was Duboscq who first made this 

 lamp in France. 



It o icn's Lamp. In this apparatus, which is represented 

 in Fig. 50, each luminous centre, instead of having only one 

 carbon, was provided with four or five, and all these carbons 

 A B, arranged vertically and circularly, were terminated by 

 small carbon cylinders in which were incorporated, in the 

 upper parts, rods of copper A B of a successively decreasing 

 length. Their lower part was connected with one of the 

 branches of the circuit, but the upper part was connected 

 with the other branch only by means of a kind of jointed 

 metallic cap which rested on them by its own weight. Their 

 height, however, being different, this cap could only touch 

 the longer one. Now, it would follow from this arrange- 

 ment that if this last were to break or be completely con- 

 sumed, the cap would fall on to the next longer one, and 

 would thus send the current through a fresh carbon, which 

 would be instantly illuminated. The latter again breaking, 

 the cap would transmit the current into a third carbon, and 

 so on until the last. Experience had shown that five carbons 

 thus arranged wera ample for an evening's illumination, and 

 during some experiments at which I was present I have twice 

 seen the lamp working at the moment of the rupture taking 

 place. 



Each of these quintuple systems of carbons was of course 

 enclosed in a hermetically sealed vessel w, from which the 

 air had been exhausted, and their difference of height was 

 calculated so that the curvature produced by the great heat 

 should not cause a division of the current. 



