Professor Joseph Henry's Invention 



have been obtained by his experiment. The 

 developments were considered at the time of 

 much importance in a scientific point of view, 

 and they subsequenty furnished the means by 

 which magneto-electricity, the phenomena of 

 dia-magnetism, and the magnetic effects on 

 polarized light were discovered. They gave rise 

 to the various forms of electro-magnetic machines 

 which have since exercised the ingenuity of in- 

 ventors in every part of the world, and were of 

 immediate applicability in the introduction of 

 the magnet to telegraphic purposes. Neither 

 the electro-magnet of Sturgeon nor any electro- 

 magnet ever made previous to my investiga- 

 tions was applicable to transmitting power to a 

 distance. 



The principles I have developed were properly 

 appreciated by the scientific mind of Dr. Gale, 

 and applied by him to operate Mr. Morse's 

 machine at a distance. 



Previous to my investigations the means of 

 developing magnetism in soft iron were imper- 

 fectly understood. The electro-magnet made 

 by Sturgeon, and copied by Dana, of New York, 

 was an imperfect quantity magnet, the feeble 

 power of which was developed by a single battery. 

 It was entirely inapplicable to a long circuit 

 with an intensity battery, and no person possess- 

 ing the requisite scientific knowledge, would 

 have attempted to use it in that connection after 

 reading my paper. 



In sending a message to a distance, two cir- 

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