68 ELECTRIC LIGHTING. 



but of larger dimensions, which however yielded results in- 

 ferior to those just mentioned. Nevertheless, they were 

 fitted up for the illumination of lighthouses on the English 

 coast. It will be seen farther on by the trials made in Eng- 

 land itself that of all the machines tried these gave the least 

 advantageous results, and we shall, therefore, say nothing 

 more about them. 



Wilde's Machine. Soft iron being, by reason of its 

 greater magnetic conductivity, capable of giving a much 

 greater maximum magnetization than the tempered steel of 

 which permanent magnets are formed, Wilde thought that 

 there might be an advantage in employing as inducing organs 

 electro-magnets instead of magnets, and that a small supple- 

 mentary magneto-electric machine, actuated by the same 

 motion as the induction machine proper, might be used to 

 magnetize them. Reasoning in this way, he was led to the 

 machine represented in Fig. 1 7, which was the starting-point 

 for all the machines subsequently designated dynamo-electric 

 machines. 



We shall, in fact, soon see that this small supplementary 

 or priming machine was unnecessary, provided the whole or 

 a part of the induced current were made to traverse the wire 

 of the electro-magnets. Nevertheless, Wilde's machine pro- 

 duced very good results, and it was the first machine of 

 small dimensions which was able to generate the electric 

 light ; but unfortunately it required a great speed of rotation, 



As shown in Fig. 17, this machine is composed of two 

 parts, of which the upper one is in a manner a miniature 

 copy of the other. The former is a Siemens' magneto- 

 electric machine, with a magnet M of 16 plates, between 

 whose poles, m tt t turns a Siemens' bobbin <?, already de- 

 scribed on page 57. This small machine is placed upon an 

 iron stage /, which serves as a connecting piece to the 

 branches A B of the inducing electro-magnet, formed of iron 

 plates wound round with thick wires, and terminated by the 



