VARIOUS GENERATORS OF ELECTRIC LIGHT. 71 



Ladd who benefited, in reputation at least, by the novelty of 

 this combination. Since the lawsuit brought by Wilde against 

 Ladd, none of the last-named gentleman's machines have 

 been made for illumination, and I am told that the model 

 exhibited in 1867 is the only one that has been shown. 



Ladd's Machine. A short time after the invention of 

 Wilde's first machine, Wheatsbone, thinking that by carrying 

 back the effect to its cause, a very minute initial magnetiza- 

 tion communicated to an electro-magnet might suffice to in- 

 crease its power indefinitely, conceived the idea of making 

 the induced current which might be produced circulate 

 through its magnetizing helix, and he was led to suppress 

 the electro-magnetic system in Wilde's machine, and to re- 

 place it by the momentary action of a very feeble voltaic 

 battery. This battery gave rise to an initial magnetization 

 in the inducing electro-magnet, and leaving in it a certain 

 amount of condensed or residuary magnetism, supplied the 

 primary cause of the disengagement of electricity which was 

 required for more energetic action. From this arrangement 

 resulted then a successive increment of the power of the in- 

 ducing electro-magnet, and consequently a strengthening of 

 the induction current, which could have no other limit than 

 the maximum saturation of the electro-magnet and the me- 

 chanical resistance offered- to the motion of the machine. 

 This idea, developed in detail by Wheatstone in a paper 

 read before the Royal Society of London on the i4th Feb- 

 ruary, 1867, was not long in being improved upon by Siemens 

 and Ladd, the former of whom conceived the idea of sup- 

 pressing the priming battery used by Wheatstone for putting 

 his apparatus into action, seeing that the mere residual mag- 

 netism of the iron or the action of terrestrial magnetism 

 would suffice to bring about the first induction. Ladd 

 adopted the plan of dividing the inductive effect between 

 two different circuits. The induction was therefore simul- 

 taneously effected in two different coils; the current pro- 



