Professor Joseph Henry's Invention 



and placed with, its north end between the two 

 arms of a horse-shoe magnet. When the latter 

 was excited by the current, the end of the bar thus 

 placed was attracted by one arm of the horse- 

 shoe, and repelled by the other, and was thus 

 caused to move in a horizontal plane and its fur- 

 ther extremity to strike a bell suitably adjusted. 



I also devised a method of breaking a circuit, 

 and thereby causing a large weight to fall. It was 

 intended to illustrate the practicabilityof calling 

 into action a great power at a distance capable 

 of producing mechanical effects; but as a de- 

 scription of this was not printed, I do not place 

 it in the same category with the experiments of 

 which I published an account, or the facts which 

 could be immediately deduced from my papers in 

 Silliman's journal. 



From a careful investigation of the history of 

 electro-magnetism in its connection with the 

 telegraph, the following facts may be established: 



1. Previous to my investigations the means of 

 developing magnetism in soft iron were imper- 

 fectly understood, and the electro-magnet which 

 then existed was inapplicable to the transmission 

 of power to a distance. 



2. I was the first to prove by actual experi- 

 ment that, in order to develop magnetic power 

 at a distance, a galvanic battery of intensity 

 must be employed to project the current through 

 the long conductor, and that a magnet surrounded 

 by many turns of one long wire must be used to 

 receive this current. 



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