156 ELECTRIC LIGHTING. 



described had been invented, and after Duboscq had pointed 

 out the defects he had found in most of the regulators then 

 in use, and even in those he had made himself, Foucault 

 invented a new form which we represent in Fig. 38, and 

 which has been hitherto generally resorted to for all experi- 

 ments of projection. This is the model which has been con- 

 structed by J. Duboscq. 



In this new system the carbon-holders B and D end below 

 in racks on which a clockwork movement acts by means of 

 a double wheel, which is arranged in such a manner that the 

 two carbons advance towards each other, and the lower one 

 D moves through twice the distance that the upper one 

 passes through. This arrangement was governed by the un- 

 equal consumption of the two carbons, which, as shown on 

 page 20, is double for the positive carbon. To obtain this 

 result, the two racks engage with the two wheels of which we 

 have spoken, and these wheels, fixed on the same axis, have 

 the number of their teeth in the proportion of 2 to i. To 

 cause this arrangement to act upon the carbons, it is only 

 necessary so to contrive matters that when the intensity of 

 the current becomes a little too feeble an electro-magnet 

 shall act on the clockwork, and that its action shall be 

 stopped when, by the approach of the carbons, the voltaic arc 

 offers less resistance. It is upon this principle that nearly 

 all the regulators of this class have been based ; but in order 

 to obtain a perfectly regular action, the problem to be solved 

 was much more complicated, and the special arrangements 

 we have now to study were necessary. 



The defect of the regulators founded on the principle we 

 have explained above, was that the electro-magnet armature 

 intended to release or to arrest the clockwork was in a state 

 of unstable equilibrium, and therefore liable to be driven 

 against one or the other of the two stops which limited its 

 play without ever being able to remain in an intermediate 

 position. In order to remedy this, the antagonistic spring R 

 of the electro-magnet E was made, not to act directly on the 



