1 7 4 RLE C 7R1C LIGHTING. 



energy, quickly produces a fresh engagement of the wheel, 

 which checks the rise of the carbon at the proper instant. 

 The slight movement of the attracted armature A, when the 

 carbons are in contact, suffices to allow the passage of 

 enough chain to bring about the separation of the carbons 

 when the circuit is closed. 



In this pattern the upper carbon is fixed, and therefore the 

 luminous point changes its position, a thing of no conse- 

 quence for ordinary illumination; but for experiments of 

 projection, the two carbons must be so arranged as to move 

 simultaneously in the proportion of 2 to i, and for this pur- 

 pose Biirgin fixes the two carbon-holders to two chains, which 

 are wound upon two pulleys of unequal diameter, mounted 

 on the axis of the large regulating wheel, so that each move- 

 ment of that wheel causes a double displacement of the car- 

 bons. An adjusting screw attached to the break allows the 

 apparatus to be made more or less sensitive. In this pattern 

 it is the weight of the upper carbon-holder which, as in 

 Serrin's regulator, brings the carbons together, and the attrac- 

 tive action of the electro-magnet first determines their sepa- 

 ration in order that an arc may be formed, and afterwards 

 .stops them so as to maintain their due interpolar distance. 



Gaiffe's Lamp. In 1850, Archereau, reflecting upon the 

 considerable space that a rod of soft iron will move within a 

 coil under the influence of the magnetic attractions, invented 

 A regulator based upon that principle. He formed one of 

 the carbon-holders of a rod, half of copper and half of iron, 

 placed within a long coil, and to properly balance the attrac- 

 tive force he used a counterpoise. This was, therefore, one 

 of the simplest of regulators, and it had the advantage of 

 being capable of lighting at a distance. In the hands of 

 .skilful experimenters, it could work well, but the movements 

 being too abrupt and the oscillation too large, it often went 

 out, and was not in fact a practical lamp. Jaspar and 

 Loiseau succeeded in lessening these defects, but it was not 



