BIOGKAPIIICAL MEMOIR OF JOSEPH HENRY. 147 



Sturgeon may be said to have first made an electro-magnet ; Uenry 

 undoubtedly made the electro-magnet what it is. Just after Barlow in 

 England had declared that there could be no electric telegraph to a long 

 distance, Henry discovered that there could be, how and why it could 

 be; he declared publicly its practicability, and illustrated it experi- 

 mentally by setting up a telegraph with such length of wire as he could 

 conveniently command, delivering signals at a distance b}^ the sounding 

 of a bell. 



Previously to his investigations the means of developing magnet- 

 ism in soft iron were imperfectly understood (even though the law from 

 which they are now seen to flow had been mathematically worked out 

 by Ohm), and the electro-magnet which then existed was inai)plicable/ 

 to the transmission of power to a distance. Henry" first rendered it ap- 

 plicable to the transmission of mechanical power to a distance; was the 

 first actually to magnetize a x>iece of iron at a distance, and by it to 

 deliver telegraphic signals. He showed what kind of battery must be 

 employed to project the current through a great length of wire, and 

 what kind of coil should surround the magnet used to receive this cur- 

 rent and to do the work.* 



For the telegraph, and for electro-magnetic machines, what was now 

 wanted was not discovery, but invention, not the ascertainment of 

 principles, but the devising of methods. These, the proper subjects of 

 patent, have been sui)i)lied in various ways and, as to the telegraph, 

 with wonderful efiliciency ; — in Europe, by the transmission of signs 

 through the motion of a magnetic needle ; in America, by the production 

 of sounds or records by the electro-magnet. Morse was among the first 

 to nndertake the enterprise, and — when directed to the right way 

 tlirough Professor Gale's acquaintance with Henry^'S published re- 

 searches — he carried the latter mode into practical and most successful 

 execution. If Henry" had patented his discovery, which he was urged, 

 but declined to do, Morse could have patented only his alphabetical mode 

 of signaling, and i)erhaps the use of relay-batteries, the latter indis- 

 pensable for long lines upon that system. 



The scientific as well as popular eifect of Professor Henry's first 

 paper in Silliman's Journal was immediate and great. With the same 

 battery that Sturgeon used he develo])ed at least a hundred times more 

 magnetism. The instantaneous production of magnets lifting four hun- 



*Sce Supplementary Note I, Leading Points in the History of tlie Tclcsvapli. 



