INCANDESCENT ' LAMPS. 1 99 



good results, on account of the multiplicity of its parts, but 

 \vhen by chance it does work regularly, the light it gives is 

 more intense than that of the Konn lamp. 



Sawyer-lHan's Lamp. This, lamp is nothing more than 

 King's or Lodyguine's in all its simplicity, except some in- 

 significant arrangements for lessening the calorific radiation, 

 and we are surprised at the long accounts we read in the 

 English journals about this lamp, which is probably not 

 better than the older ones. In this system, the vessel con- 

 taining the incandescent carbon is filled with nitrogen to 

 avoid combustion and the deposition of volatile products on 

 the surface of the vessel. The carbon itself is rather short ; 

 its resistance does not exceed 0*95 ohm, and each light is 

 supplied with a derivation, in order that the conditions of the 

 distribution of the current may not be changed when any one 

 of the lamps is extinguished. The commutator used for light- 

 ing and extinguishing the lamp is, moreover, arranged in such 

 a manner that the current gains its full intensity only by 

 degrees, and after having passed through successively weaker 

 resistances. It is, according to Sawyer- Man, from neglect of 

 this precaution that the carbons of incandescent lamps are 

 so soon spoiled. Finally, an electro-magnetic register is in- 

 cluded in the circuit, and has the same effect as a gas-meter. 



We shall not speak of the system of distributing the current 

 among all these lamps, for it is founded on the principle of 

 derivation, and is identical with that of Werdermann, which 

 we shall presently consider. A detailed description of this 

 lamp may, however, be seen in the Telegraphic Journal Q{ ist 

 January, 1879. We think it unnecessary to say more about 

 it, than to express our surprise that English and American 

 inventors trouble themselves so little about the earlier in- 

 ventions. 



E. Reynier's Lamp. We have seen, on page 146, the 

 principle on which this lamp is based. The lamp is the most 



