THE ELECTRIC LIGHT 455 



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 mag- 

 netic saturation. Such a magnet and armature are able to 

 produce currents of extraordinary power, and if an elec- 

 tric lamp be introduced into the common circuit of mag- 

 net and armature, 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 ex- 

 citing 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 elec- 

 tricity 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 lighthouse 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 apparatus 



* 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. 



