THE ELECTRIC LIGHT. 561 



Reaction thereon of Currents induced by the Magnet itself." Both 

 papers, which dealt with the same discovery, and which were illustrated 

 by experiments, were read upon the same night, viz., the 14th of Feb- 

 ruary. The whole field of science hardly furnishes a more beautiful 

 example of the interaction of natural forces than that set forth in these 

 two papers. You can hardly find a bit of iron — you can hardly pick 

 up an old horseshoe, for example — that does not possess a trace of 

 permanent magnetism ; and from such a small beginning Siemens and 

 Wheatstone have taught us to rise by a series of interactions between 

 magnet and armature to a magnetic intensity previously unapproached. 

 Conceive the Siemens armature placed between the poles of a suitable 

 electro-magnet. Suppose this latter to possess at starting the faintest 

 trace of magnetism ; when the armature rotates, currents of infinitesimal 

 strength are generated in its coil. Let the ends of that coil be con- 

 nected with the wire surrounding the electro-magnet. The infinitesimal 

 current generated in the armature will then circulate round the magnet, 

 augmenting its intensity by an infinitesimal amount. The strengthened, 

 magnet instantly reacts upon the coil which feeds it, producing a cur- 

 rent of greater strength. This current again passes round the magnet, 

 which immediately brings its enhanced power to bear upon the coil. 

 By this play of mutual give and take between magnet and armature, 

 the strength of the former is raised in a very brief interval from almost 

 nothing to complete magnetic saturation. Such a magnet and arma- 

 ture are able to produce currents of extraordinary power, and if an elec- 

 tric lamp be introduced into the common circuit of magnet and arma- 

 ture, we can readily obtain a most powerful light.' By this discovery, 

 then, we are enabled to avoid the trouble and expense involved in the 

 employment of permanent magnets ; we are also enabled to drop the 

 exciting magneto-electric machine, and the duplication of the electro- 

 magnets. By it, in short, the electric generator is so far simplified, 

 and reduced in cost, as to enable electricity to enter the lists as the 

 rival of our present means of illumination. 



Soon after the announcement of their discovery by Siemens and 

 Wheatstone, Mr. Holmes, at the instance of the Elder Brethren of the 

 Trinity House, endeavored to turn this discovery to account for light- 

 house purposes. Already, in the spring of 1869, he had constructed a 

 machine which, though hampered with defects, exhibited extraordinary 

 power. The light was developed in the focus of a dioptric apparatus 

 placed on the Trinity Wharf at Blackwall, and witnessed by the Elder 

 Brethren, Mr. Douglass, and myself, from an observatory at Charlton, 

 on the opposite side of the Thames. Falling upon the suspended haze, 

 the light illuminated the atmosphere for miles all round. Anything so 

 sunlike in splendor had not, I imagine, been previously witnessed. The 



^ In 1867 Mr. Ladd introduced the modification of dividing the armature into two 

 separate coils, one of which fed the electro-magnets, while the other yielded the induced 

 currents. 



