THE ELECTRIC LIGHT. 67 1 



where the two pieces touch. When a strong battery 

 of from 40 to 80 large Bunsen elements is used, and 

 two pointed pencils of carbon, connected with the 

 terminals, are brought close together, light of most 

 dazzling splendour is emitted by the two points, such 

 as cannot be obtained from any other artificial source. 

 This ' electric light ' is now frequently used for illumi- 

 nating purposes on a grand scale, but is rather expen- 

 sive ; for not only is a strong current required for it, 

 but also a somewhat complex apparatus for maintain- 

 ing the distance between the two carbon points, which 

 is at every moment, while the current ]asts, increased 

 by two causes. One of them is the wasting away of 

 the carbon by the combustion that is going on, the 

 other is that by the action of the current solid carbon 

 particles are constantly transferred from one pole to 

 the other; now it happens that the positive current 

 has more power to transfer matter than the negative, 

 and as a portion of the transferred particles is burnt, 

 it follows that the positive pole becomes blunt, and 

 even hollowed out, while the negative carbon pencil 

 remains pointed by the slow deposition of carbon dust, 

 although it does not really gain in size. The wasting 

 away, particularly of the positive pole, in a short 

 time renders the distance between the poles too great 

 to allow of the passage of the current, and the light 

 would be extinguished but for a contrivance which acts 

 as c regulator.' The transference of matter accounts 

 for the fact that in producing a powerful electric light 

 the points are first brought in contact, and are then 

 separated again a few millimetres, without breaking 

 the circuit. The carbon particles constitute a conduct- 



