ELECTRIC LIGHTING. 307 



tvith either alternating or continuous currents ; secondly, 

 great diversibility and complete independence of the several 

 lights, and long duration without change of carbons ; and 

 lastly, the extreme facility with which any ordinary workman 

 or servant can renew the carbons when necessary, without 

 extinguishing the lights.' The last-named advantage results, 

 it need hardly perhaps be said, from the use of two carbons 

 to form each point. One can be removed, the other 

 remaining to keep the voltaic arc intact until a new carbon 

 has been substituted for its fellow ; then it in turn can be 

 replaced by a new carbon, the new carbon already inserted 

 keeping the voltaic arc intact. 



The six lamps at the ' Times ' office thoroughly illuminate 

 the room, and give light for working the eight Walter presses 

 used in printing the paper. The light has been thus used 

 since the middle of last October, and it is said that other 

 rooms in the building are shortly to be illuminated in the 

 same manner. ' Each lamp is enclosed .in an opal globe of 

 about four inches in diameter, and so little heat is given off, 

 that the hand can be placed on the globe without incon- 

 venience, even after the light has been barning for some 

 time.' 



In the Wallace lamp there are two horizontal plates of 

 carbon, about nine inches in diameter, instead of mere 

 carbon points. When the current is passing, these carbon 

 plates are separated by a suitable small distance which 

 remains unchanged. The electric arc, being started at the 

 point along the edge of the carbons where there is least 

 resistance to the passage of the current, gradually passes 

 along the edge of the carbons as combustion goes on, 

 changing the position of the place of nearest approach and 

 consequently of least resistance. The light will thus burn 

 for many hours (even for a hundred with large carbon plates), 

 and any number of lights up to ten can be worked from the 

 machine. The objection to the Wallace lamp is, that the 

 light does not remain at one point, but travels along the 

 whole extent of the carbons. It will not be easy to design 



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