220 ELECTRIC LIGHTING. 



two brass uprights, one of which A c is double-jointed, and 

 ends in a shoulder c that will exactly fit the piece to be 

 placed between it and B. A strong spring R presses c 

 towards B. The two pieces B and c are provided with cylin- 

 drical grooves which receive the metallic terminals of the 

 candle. As these pieces are electrically insulated from each 

 other and provided with binding screws, it is easy to connect 

 the two carbons into circuit. 



Several plans may be used for obtaining continuity of 

 illumination ; the simplest and best is to connect one of the 

 terminals of each lamp to a commutator, so that, after the 

 combustion of a candle, the current may be made to pass 

 into the next one by simply turning a handle. This commu- 

 tator, in the apparatus at the Avenue de V Opera, is placed 

 within the support of the lamp, and an attendant comes 

 every hour and a half and turns the handle. This commu- 

 tator is double, in order to make a double change, when two 

 candles are burnt in the same lamp, as in the lights at the 

 Place de r Opera. The construction of the apparatus is very 

 simple ; it consists merely of a wooden disc on which are 

 fixed in a circle as many metallic plates as there are candles; 

 a handle with a spring turns on a metal pillar in the centre 

 of the disc, and the spring pressing against the plates esta- 

 blishes a connection between the central pillar and the plate 

 connected with such candle as may be required. 



Besides this plan several automatic arrangements have 

 been invented, but they have not been generally adopted 

 in practice, which has retained the commutators just de- 

 scribed. One of these arrangements, represented in Fig. 64, 

 consisted of a bent lever M o ;;/ turning at o and carrying at 

 one end the platinum wire /"leaning against the insulator of 

 the candle A' B', and at the other end provided with a con- 

 tact piece M, which, by touching another piece P, closed the 

 circuit through the next candle A B. A spring r acting on 

 the lever kept the wire / (by which the contact of M and P 

 was prevented), pressed against the candle; but when the 



