180 Description of an Electromotive Engine. 



Fig. I. represents the poles of a magnet with its keeper; 

 both being electro-magnets. That from which this figure is 

 taken is a bar of soft iron, two inches square, and weighs about 

 801bs. The apparatus by which the movement is produced 

 and regulated, is placed as represented in the drawing. A. B. 

 is a board firmly wedged or screwed between the arms of the 

 magnet. C. D. a copper bar, which moves on a pivot at P. 

 To this bar a permanent communication is made with one 

 side of the battery, say the zinc side. The copper side com- 

 municates with both the magnet 1, and keeper 2, by the cop- 

 per strap O. To the nut at E., the strap intended to com- 

 municate with the zinc side is screwed, and to E. is in like 

 manner attached the wire from the keeper intended to 

 communicate also with the zinc side. The bar D. strikes 

 alternately E. and F. as it is acted upon by the keeper; 

 which it does as follows : 



It will be observed that one side of the magnet, and one 

 side also of the keeper, are permanently connected with the 

 copper side of the battery, by the copper strap O. Now, 

 when the bar C. D. is made to touch E., the magnet receives 

 the whole of the current from the battery ; and when the 

 same bar touches F., the current passes only through the 

 keeper. Therefore, when the magnet is rendered magnetic, 

 it attracts the keeper, which is then not magnetic ; and when 

 the current is instantaneously shifted to the keeper, it is sud- 

 denly repelled by the residuum remaining for a moment in 

 the magnet, as already described. 



The current is thus thrown alternately on the electro- mag- 

 net and keeper, and this is effected by the movement of the 

 latter. It is absolutely necessary that the copper bar D. 

 should remain in contact with E. during the movement of the 

 keeper from its greatest distance, till it actually strikes the 

 magnet. Let us suppose, that the copper bar D. is in contact 

 with E. ; the magnet will now attract the keeper, and when 

 it arrives within, say the 20th of an inch of the magnet, it 



