SOURCE OF THE ILLUMINATION. 169 



are properly joined, the fine wire within the cartridge is 

 instantaneously ignited, and the gunpowder or other ex- 

 plosive material is fired. 



When the interruption in the circuit is made under cer- 

 tain circumstances and iu a certain way, the intervening 

 space is filled with extremely minute particles, which are 

 detached from the solid substance at one side of the inter- 

 val and driven across to the other side in a state of intense 

 heat and incandescence. This especially takes place when 

 the two terminations on each side of the interval are formed 

 of cones of carbon. In this case particles of the carbon, so 

 minute as to be individually entirely invisible, become de- 

 tached from one side and pass across through the air to the 

 other in a state of incandescence so intense as to furnish a 

 light which surpasses almost every other artificial light in 

 brilliancy. 



And this is the famous electrical light. 



The charcoal points used are actually very small. The 

 engraving, however, shows the effect which is produced, 

 and the result of it in modifying the forms of the points, 

 as seen greatly magnified. The globules of melted matter 

 which appear attached to the cones come from the fusion 

 of the earthy impurities in the carbon. 



Although the light is thus derived from incandescent 

 particles of carbon, it is not at all due to heat produced by 

 the combustion of them, as is, in a great measure, the case 

 with the light which comes from a common fire that is 

 to say, the heat which renders them incandescent is not 

 the heat derived from their own combination with oxygen, 

 but from that developed by the electricity alone, which is 

 vastly more intense than any heat which their combustion 

 would produce. The evidence of this is that the electric 

 light is equally vivid in a vessel exhausted of aii\ as shown 

 in the engraving on the following page. 

 H 



