266 HENRY AND THE TELEGEAPH. 



1798. D. F. Salva, iu Spain, appears to have successfully worked an 

 electric telegraph through the unprecedented distance of twenty- six 

 miles. "The Madrid Gazette of November 25, 1796, states that the 

 Prince de la Paix, having heard that M. D. F. Salva had read to the 

 Academy of Sciences a memoir upon the application of electricity to tele- 

 gra.phiug, and presented at the same time an electric telegraph of his 

 own invention, desired to examine it; when being delighted with the 

 promptness and facility with which it worked, he presented it before the 

 king and court, operating it himself. Some useful trials were made and 

 published in Voigfs Magazine. Two j^ears after, tlie Infanta Don Anto- 

 nio constructed a telegraph of great extent on a large scale, by which 

 the young prince was informed at night of nesvs in which he was much 

 interested. He also invited and entertained Salva at court. According 

 to Humboldt, a telegraph of this description was established in 1798, 

 from Madrid to Aranjuez, a distance of 26 miles."* 



1816. Francis Ronalds constructed at Hammersmith, England, an 

 experimental telegraph line of a single wire, operated by an electrical 

 machine, or small Leydeu jar. "He proved the practicability of such a 

 scheme by insulating eight miles of wire on his lawn at Hammersmith. 

 In this case the wire was insulated in the air by silk strings. . . . 

 Mr. Eonalds fixed a circular brass plate upon the seconds arbor of a 

 clock which beat dead seconds. This ]:>late was divided into twenty 

 equal parts, each division being worked by a figure, a letter, and a pre- 

 l^aratory sign. The figures were divided into two series of the units, 

 and the letters were arranged alphabetically, omitting J, Q, v, w, x, 

 and z. In front of this was fixed another brass plate (which could be 

 occasionally turned round by hand), and which had an aperture that 

 would just exhibit one of the figures, letters, and preparatory signs. In 

 front of this plate was suspended a pith-ball electrometer from a wire 

 which was insulated and which communic^ited on one side with a glass 

 cylinder machine. At the farther end of the wire was an apparatus 

 exactly the same as the one now described, and the clocks were ad- 

 justed to as perfect synchronism as possible. Hence it is manifest that 

 when tlie wire was charged by the machine at either end, the electro- 

 meters at both ends diverged, and when it was discharged they collapsed 

 at the same instant ; consequently if it was discharged at the moment 

 when a given letter, figure, and sign on the plate appeared through 

 the aperture, the same letter, figure, and sign would appear also at the 



* The EJectro-MafivcUc TeJcf/raph, by Laurence TnrnbuU, 8vo. 2(1 ed. Pliilada. 1S53, 

 pp. 21, 22. Voigt's Maaazln, etc. vol. xi, part 4. The same telegraphic feat is attrib- 

 uted to B<^taiieoTirt. ''Gauss makes mention of a eonuunnication irom Hnniiioldt, 

 according to Avliieli Bdtanconrt, in 171)8, established a connnnnication between jMadrid 

 and Araiijnez, a distance of 2G miles, by means of a wire through which a Leyden jar 

 used to be discharged, which was intended to be used as a telegraphic signal." (Stnr- 

 o-eon's Annals of EJcctridtii, etc. March, 18:^9, vol. iii, p. 44ri.) This is probalily a mis- 

 apprehension; as Augustine B<5taucourt (more correctly Betheuconrt), a S])anis]i engi- 

 neer, in 1798, devised nnd exhiluted to the National Institute an improvement in the 

 mechanical semaphore. (Brewster's i?fZinZ*ur</7i Encycloiiosdia, 1830, art. "Telegraph,' 

 vol. xviii, p. 535.) 



