INCANDESCENT LAMPS. 209 



in the third position, the circuit is interrupted, and the other 

 lamps benefit by the portion of the current that was pre- 

 viously passing through the lamp. 



Besides the resistances just spoken of, there are others 

 placed in the course of the positive wire of each derivation, 

 which are indicated in Fig. 57, and serve to change the 

 brilliancy of any particular lamp. 



This system of electric lamp has lately been used in 

 London for lighting the South Kensington Museum, where 

 it is said to have produced a well-spread light of a fine 

 quality, an agreeable softness, and a remarkable steadiness. 

 (See the journal La Lumiere eleclrique of the i5th July, 

 1879, p. 72.) 



Some very successful experiments were also made at Paris, 

 in which six to eight lamps were lighted by the current of 

 an Alliance machine. It is asserted that it will be possible 

 to light a much greater number with lamps of a smaller 

 pattern and with a particular arrangement of the machine. 

 We shall wait and see the result for ourselves before pro- 

 nouncing on this matter. We have just learnt that with a 

 Gramme machine, driven by a gas engine of 6 horse-power, 

 it has been found possible to light 1 5 Werdermann lamps, the 

 carbons of which were 4-5 millimetres in diameter, each lamp 

 giving a light of 25 Carcel lamps. It was, however, a new 

 form of this kind of lamp which gave this result, and this 

 form is not sufficiently known for us to describe it here. 

 (See ^ T ote I> at the end of this volume.) 



Trouve's form of Reynier's Lamp. Trouve' has just 

 given a new arrangement to Reynier's lamp, which is some- 

 what that of Werdermann, and at once rather practical and 

 economical. Fig. 59 will give a precise idea of it. The 

 small carbon E, which gives the incandescence, is inclosed 

 in a long tube with a slit all its length, which allows the 

 movable portion D to push the fine carbon against the mas- 

 sive cylinder D under the influence of a counterpoise P pro- 



