The Three Secretaries 133 



Davy and Morse. The modern, or electro-magnetic, tele- 

 graph was not proposed, however, until 1820, after the revi- 

 val by Oersted of the knowledge of the power of the galvanic 

 current to deflect a suspended magnetic needle. 



The " needle-telegraph," that in which intelligence is trans- 

 mitted by the motion of the galvanoscopic indicator, was the 

 form to which the attention of European theorists and in- 

 vestigators was now directed. Ampere, before 1823, had 

 worked out the theory of a telegraph with several needles. 

 The first operative system of this type was that devised in 

 1828 by Triboaillet, who employed a single wire and a gal- 

 vanoscopic indicator. Schilling exhibited in Russia in 1832 

 a single-circuit instrument with thirty-six needles. This was 

 improved and used in experimental work at a distance of 

 9000 feet in Gottingen, in 1833, by Gauss and Weber, who 

 utilized the discoveries of Henry and Faraday.^ The needle- 

 indicator used by these investigators was essentially the same 

 as that still occasionally employed, especially in connection 

 with long submarine cables. 



The other form of telegraph is that in which sounds and 

 permanent signs are made by the attraction of an electro- 

 magnet. It was this system which Henry devised and used 

 in a simple form, and this which Morse and his staff, 

 acting avowedly under the advice of Henry, were first to 

 develop into a practical agency for the transmission of 

 words. Henry was the first, as already remarked, to demon- 

 strate the fact that a galvanic current could be transmitted to 

 a great distance with so little diminution of force as to pro- 

 duce mechanical effects adequate to telegraphic uses. He 

 actually constructed, and operated in Albany, as early as 

 1830, the first electro-magnetic machine for producing at will 

 sounds that could be heard at a distance, and published at 



1 Gray, Thomas, "Proceedings and Addresses, Patent Centennial Celebrations," page i8i. 



