Description of an Electro-motive Engine. 181 



strikes the end of the long brass screw M. (passing through 

 CD.) which throws the copper bar CD. upon F. ; thus 

 shifting the current from the magnet to the keeper. The 

 keeper is now repelled, and as it reaches the required distance 

 or angle, regulated by the screw L., to which it is attached 

 by the chain S., it necessarily throws the copper bar D. back 

 against E., shifting the current again to the magnet which 

 attracts the keeper as before ; and in this manner the move- 

 ment is continued. The keeper is attached to the screw L. 

 by twine or a chain, so as that it may not move the copper 

 bar C. D. till it arrives at the required angle or distance. 



The movement of the bar CD. between E. and F. may 

 easily be regulated by the screw F. It need not exceed the 

 20th of an inch, or it may be less ; all that is required being 

 to break metallic contact. The screw M. can easily be ad- 

 justed so as to make the keeper, when it comes in contact 

 with it, shift the bar C D. from E. to F. ; but this adjust- 

 ment must be accurately made, to insure regularity in the 

 movement. As the keeper does not shift the current from 

 the magnet till it is within less than the 20th or 40th 

 part of an inch from actual contact, we shall find that actual 

 contact does always take place before the keeper is thrown 

 off by the magnetism induced in it acting upon the residuum 

 remaining for a moment in the magnet. 



When the keeper is not attached to the fly wheel, it strikes 

 the magnet with great force and noise ; but there is no noise 

 when it is loaded or has work to do. It may be made to 

 strike 150 to 200 times in a minute; and never adheres to 

 the magnet. 



With regard to the action of the keeper upon the fly wheel, 

 it will be seen by the annexed figure that it is performed by 

 a contrivance different from a crank. The crank can hardly 

 be applied with advantage where the impulse is repeated 

 several times during onejevolution of the wheel. The motion 

 of the fly wheel is produced by repeated pulls upon the rim 



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