1857] WRITINGS OF JOSEPH HENRY. 435 



should state however that the arrangement I have described 

 was merely a temporary one, and that I had no idea at the 

 time of abandoning my researches for the practical applica- 

 tion of the telegraph. Indeed, my experiments on the 

 transmission of power to a distance were suspended by 

 the investigation of the remarkable phenomena (which I 

 had discovered in the course of these experiments) of the 

 induction of a current in a long wire on itself, and of which 

 I made the first mention in a paper in Silliman's Journal 

 in 1832.* 



I also devised a method of breaking a circuit and thereby 

 causing a large weight to fall. It was intended to illustrate 

 the practicability of calling into action at a distance a great 

 power capable of producing mechanical effects; but as a 

 description 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 follow- 

 ing facts may be established : 



1. Previous to my investigations the means of developing 

 magnetism in soft iron were imperfectly 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 experiment that in 

 order to develop magnetic power at a distance a galvanic bat- 

 tery 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. 



3. I was the first to actually magnetize a piece of iron at 

 a distance, and to call attention to the fact of the applica- 

 bility of my experiments to the telegraph. 



4. I was the first to actually sound a bell at a distance by 

 means of the electro-magnet. 



* [Silliman's American Journal of Science, July, 1832, vol. xxil, p. 408. 

 See ante, vol. i, p. 79.] 



