THE ELECTRIC LIGHT 469 



unconnected with the water-pipes, the circuit is incom- 

 plete and no current will flow; but if any part of the 

 main, however distant from the battery, be connected with 

 the adjacent water-pipes, the circuit will be completed and 

 the current will flow. Supposing our battery to be at 

 Charing Cross, and our rod of copper to be tapped oppo- 

 site Somerset House, a wire can be carried from the rod 

 into the building, and the current passing through the 

 wire may be subdivided into any number of subordinate 

 branches, which reunite afterward and return through the 

 water-pipes to the battery. The branch currents may be 

 employed to raise to vivid incandescence a refractory 

 metal like iridium or one of its alloys. Instead of being 

 tapped at one point, our main may be tapped at one hun- 

 dred points. The current will divide in strict accordance 

 with law, its power to produce light being solely limited 

 by its strength. The process of division closely resembles 

 the circulation of the blood; the electric main carrying 

 the outgoing current representing a great artery, the water- 

 pipes carrying the return current representing a great vein, 

 while the intermediate branches represent the various ves- 

 sels by which the blood is distributed through the system. 

 This, if I understand aright, is Mr. Edison's proposed 

 mode of illumination. The electric force is at hand. 

 Metals sufficiently refractory to bear being raised to vivid 

 incandescence are also at hand. The principles which reg- 

 ulate the division of the current and the development of 

 its light and heat are perfectly well known. There is no 

 room for a "discovery," in the scientific sense of the term, 

 but there is ample room for the exercise of that mechan- 

 ical ingenuity which has given us the sewing machine and 

 so many other useful inventions. Knowing something of 



