ELECTRO-MAGNETIC ENGINES. 713 



consisting of horse-shoes of considerable size, round 

 which a vast quantity of stout copper wire is coiled, 

 weights of several thousand kilogrammes may -be sup- 

 ported. 



The attraction of electro-magnets has been variously 

 applied for the construction of electro-magnetic engines 

 for the production of continued motion. On a small 

 scale the current will often render great service as a 

 source of motion, as, for example, for producing rotatory 

 motion in a siren, stirring a liquid by means of a paddle 

 wheel in a small vessel, or for similar purposes. But for 

 performing a large amount of work electric engines ha\ 7 e 

 not proved themselves equal to steam engines, because 

 their effect does not increase in proportion to their 

 dimensions, and also because the maintenance of 

 batteries capable of producing sufficiently strong cur- 

 rents is much more expensive than the fuel required 

 for heating the water in a steam-boiler. 



A very simple contrivance for producing continuous 

 motion by electro-magnetism is represented in fig. 362 

 A, in which a b represents a horse-shoe electro-magnet 

 with its poles turned downwards and fixed to a small 

 wooden - board. Another electro-magnet, c d, which is 

 straight, can turn within the legs of the horse-shoe 

 about a vertical spindle with conical pointed ends, of 

 which the upper one fits into a small cavity in the 

 screw/, which passes through the horse-shoe, while the 

 lower rests in a similar cavity of the metal piece e. 

 When c d turns, the ends of the spiral coiled round it 

 glide along the metal pieces g and A, each of which is 

 nearly a semicircle. The terminals of the battery are 

 connected with the apparatus at i and k by binding 



