1 82 ELECTRIC LIGHTING. 



their extremities burned away, they were pushed forward by 

 the springs, and as they became thin by burning at the ex- 

 tremities only, the cold part always remained within the re- 

 fractory cone. In Rapieff's system the same effect is pro- 

 duced, but there are no refractory cones, these being replaced 

 by four sticks of carbon joined at the ends two by two at an 

 acute angle, and so arranged one above the other as to form 

 two angular systems in planes perpendicular to each other. 

 The points of contact which form the electrodes are sepa- 

 rated one from the other by the distance desired for forming 

 the voltaic arc. Counterpoises with pulleys are arranged to 

 push the carbons of each system one against the other, and 

 then, as these carbons are consumed, they constantly advance 

 towards the common point of intersection, which remains 

 always at the same place. 



Fig. 47 represents this regulating system, the carbons of 

 Avhich, a a', b b\ seem to form an X, with this difference, that 

 the two lower carbons are placed in a plane perpendicular 

 to that in which the upper ones are placed. The voltaic arc 

 is produced at c, between the upper and the lower pairs of 

 points. As the carbons are consumed, they slowly move 

 nearer to each other in each couple, under the influence of 

 a counterpoise w, which, through the cords and the pulleys 

 VJ f h d a! a e g d' b' b, pushes the sticks of carbon against 

 each other. This counterpoise is guided in its course by 

 two columns s s', which at the same time serve as conductors 

 for transmitting the current to the two systems of electrodes 

 a a', b b', supported also by the two metallic arms d h, d' g. 

 As the upper carbons are to be connected with the positive 

 pole, they fire of course longer than the lower. This arrange- 

 ment is completed by an electro-magnetic system enclosed in 

 the base of the apparatus ; and its office is, when the current 

 passes and the four sticks of carbon are in contact, to sepa- 

 rate the two systems to the distance necessary for the for- 

 mation of the arc. This effect is produced by means of a 

 cord attached to the electro-magnetic armature, which cord, 



