ADDRESS OF PROF. A. M. MAYER. 487 



view, and they subsequently furnished the means by which magneto- 

 electricity, the phenomena of dia-magnetism, and the magnetic effects 

 in polarized light were discovered. They gave rise to the various 

 forms of electro-magnetic machines which have exercised the inge- 

 nuity of inventors in every part of the world, and were of immediate 

 applicability in the introduction of the magnet to telegraphic pur- 

 poses. Neither the electro-magnet of Sturgeon nor any electro- 

 magnet ever made jn-evious to my investigations waa applicable to 

 transmitting power to a distance." 



Henry however was not satisfied with the mere statement that 

 his discovery was "directly applicable to Mr. Barlow's project of 

 forming an electro-magnetic telegraph ;" he actually constructed an 

 electro-magnetic telegraph. Sometime during the year 1831, "I 

 arranged," says he, " around one of the upper rooms of the Albany 

 Academy a wire of more than a mile in length, through which I 

 was enabled to make signals by sounding a bell. The mechanical 

 arrangement for effecting this object was simply a steel bar, perma- 

 nently 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 hori- 

 zontal plane and its further end to strike a bell suitably adjusted." 



This was the first electro -magnetic telegraph which had worked 

 through so great a length of wire; it was the first electro-magijetic 

 telegraph in which an electro-magnet had worked successfully; it 

 was the first "sounding" electro-magnetic telegraph. 



On this occasion we have not the time to enter into a discussion 

 of the relative parts played by Henry and Morse in the invention of 

 the electro-magnetic telegraph ; nor do I think such a course neces- 

 sary. Henry's own words as given in his "Statement in relation 

 to the history of the electro-magnetic telegraph," and published by 

 the Regents of the Smithsonian Institution in 1857, give all that is 

 required to a just understanding of the relations of these two dis- 

 tinguished men to this invention. 



"The principles," says Henry, (referring to his discoveries in 

 electro-magnetism of which I have just given an account,) "I had 



