144 ELECTRIC LIGHTING. 



kind of the contrary electricities, which, by charging the- 

 condensers, cause the illumination of the plates of kaolin, oa 

 which streaks of black lead extend from one clip to the other- 



Lodygiiine and Kosloff 's System. Of the various methods 

 used for obtaining luminous effects by the narrowing of 

 the section, : pf a good conductor, that contrived by Lody- 

 guine and Koslqff had given some very interesting results 

 These results even made some noise in 1874, for the effects 

 were nearly similar to those we have just mentioned; but in 

 order to produce them a. .much greater electrical force was 

 required, and the portions of the apparatus brought to a 

 white heat, being made of retort-coke of Very narrow section, 

 did not present the desired conditions of solidity and stability. 



In this system these little needles of carbon were cut out 

 of carbon prisms of at least i centimetre across, and were 

 fixed between two insulated clips connected with the two- 

 branches Of the circuit, as in JablochkofPs system.* In 

 order to prevent their combustion they were enclosed in 

 vessels free from air, or simply hermetically sealed, so that 

 the oxygen of the enclosed air should not be renewed. 

 With a powerful Alliance machine four luminous foci could,, 

 it is said, be obtained in this way, and the lighting power was 

 very satisfactory. Unfortunately these carbons were fre- 

 quently broken, and it was quite a task to replace them. To 

 obviate this inconvenience several ingenious arrangements 

 were invented, of which we shall speak farther on; but all 

 these systems have scarcely yielded anything very satisfactory 

 from a practical point of view. 



The slender rod of carbon was in fact consumed parti- 



* It -seems that the connection of the carbons intended to become 

 red hot with tlic wires of the circuit was one of the difficulties which 

 checked 'Lodyguine and Kosloff. In fact, by making the wire penetrate into 

 the carjiop, the latter was broken, on account of the difference of the ex- 

 pansion pf the metal and that of the carbon, and again the metal by touch- 

 ing the parts'qf the carbon heated to whiteness was melted. Kosloff, after 

 many experiments, has, it appears, avoided these difficulties by using a 

 special'metal to form the supports of the carbon rods. 



