434 WRITINGS OF JOSEPH HENRY. [1857 



the transmission of or calling into action power at a distance. 

 The first was carried into execution in the construction of 

 the machine described in Silliman's Journal in 1831;* and 

 for the purpose of experimenting in regard to the second, I 

 arranged around one of the upper rooms in the Albany 



Academy a wire of more than 

 a mile in length, through which 

 I was enabled to make signals 

 by sounding a bell. (Fig. 7.) 

 The mechanical arrangement 

 for effecting this object was 

 simply a steel bar, permanentl}' 

 magnetized, of about ten inches 

 in length, supported on a pivot, 

 ^^°- '^- 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 further extremity to strike a bell 

 suitably adjusted. 



This arrangement is that which is alluded to in Professor 

 Hall's letterf as having been exhibited to him in 1832. It 

 was not however at that time connected with the long wire 

 above-mentioned, but with a shorter one put up around the 

 room for exhibition. 



At the time of giving my testimony I was uncertain as to 

 when I had first exhibited this contrivance, but have since 

 definitely settled the fact by the testimony of Hall and others 

 that it was before I left Albany, and abundant evidence can 

 be brought to show that previous to my going to Princeton 

 in November, 1832, my mind was much occupied with the 

 subject of the telegraph, and that I introduced it in my 

 course of instruction to the senior class in the Academy. I 



* [Silliman's American Journal of Science, July, 1831, vol. xx, pp. 

 340-343. See ante, vol. i, p. 54.] 



f [See Appendix B, at the end of this paper ; and also Proceedings of the 

 Albany Institute, January 13, 1858; vol. iv, pp. 244, 245.] 



