Figure 9. — Henry's "telegraph" signal of 

 1 83 1 -1 832. From Animal Report of the Smith- 

 sonian Institution . . . Jor the Year Eroding June jjo, 

 1857, 1858, p. 105, fig. 7. 



During the 1830"s a number of inventors rec- 

 ognized the possibility that a binary code might 

 reduce the number of wires necessary to transmit 

 electrical telegraphs. Much earlier Schweigger '^ 

 had suggested that modifying Soemmerring's system 

 by the use of a binary code could eliminate many 

 of the wires required in the Soemmerring device, 

 but the first to attempt to put a binary code into prac- 

 tice in an electromagnetic signaling system were two 

 German physicists — Carl F. Gauss and his assistant, 

 Wilhelm Weber. ^^ Gauss and Weber also understood 

 how to transmit signals over distances of a mile or so. 



It was while Gauss was studying the magnetism 

 of the earth that he found that some of the equipment 

 employed in his research could also be used for a 

 telegraph. Gauss had shown an interest in tele- 

 graphs before this; he was one of the many visitors 

 who, during the 1810"s, had stopped in Munich to see 

 Soemmerring's apparatus, and in the early 1820's 

 he had invented a heliograph, or optical telegraph, 

 that used a binary code. 



'2 J. S. Schweigger, "Uber Sommerring's elektrischen Tele- 

 grapher!, Ill: Nachschreiben des Herausgeber's," Schweig- 

 gei's Journal, 1811, vol. 2, pp. 238-247. 



13 C. F. Gauss, Werke, Berlin, 1929, vol. 11, Abt. 2, Abh. 2, 

 passim; Ernst Feyerabend, Der Telegraph von Gauss und Weber im 

 Werden der elektrischen Telegraphie, Berlin, 1933. It should be 

 noted that in describing the Gauss and Weber telegraph, this 

 work uses units of the local German foot. 



Gauss had begun his observations on the earth's 

 magnetism with equipment that he set up in the 

 Gottingen astronomical observatory in 1832. Early 

 in 1833 Gauss and Weber converted one of their 

 instruments into a needle galvanometer so that 

 they could test the validity of Ohm's work on circuits. 

 A bar magnet weighing about a pound constituted 

 the needle; the coil consisted of 300 feet of wire; a 

 chemical battery supplied the power; and a commuta- 

 tor could reverse the current in the coil and make 

 the needle swing to the right or left. Weber set up 

 a double copper line that ran between the astro- 

 nomical observatory and the laboratory of the 

 University of Gottingen — a distance of 8,000 feet. 

 Gauss and Weber soon found that their circuit 

 could be used for other purposes as well as for testing 

 Ohm's theories. '■* At first it was used to synchro- 

 nize the clocks between the two buildings, but by 

 Easter 1833 it was part of a communications system 

 that was occasionally used for sending words and 

 even phrases. For an illustration of a later telegraph 

 by Gauss and Weber, see figure 10. 



In the ineantime funds had been obtained by the 

 University of Gottingen for a magnetic observatory, 

 which was in operation by 1834. The same line 

 was extended several hundred feet from the astro- 

 nomical observatory to the magnetic observatory, 

 and a galvanometer with a 4-pound needle and a coil 

 of 1,100 feet of wire were placed in the new building. 

 By the following year that galvanometer had been 

 moved to the laboratory and a new one set up in the 

 astronomical observatory. The needle for the new 

 galvanometer was 1 .2 meters long and weighed about 

 25 pounds. It was hung by a bifilar suspension in 

 order to increase the speed of its response, and the 

 needle was moved inside a multiplier of 2,700 feet of 

 fine wire. The chemical battery, which produced a 

 gradually decreasing current, was replaced by a coil 

 that could induce an electric current whenever it was 



" Gdltingische gelehrte Anzeigen, December 27, 1832, vol. 2, 

 pp. 2049-2058; Gottingische gelehrte Anzeigen, August 9, 1834, 

 vol. 2, pp. 1265-1274; also reported in Dinglers polytechnisches 

 JournaL 1835, vol. 55, pp. 392-394, and Annalen der Physik und 

 Chemie, 1834, vol. 32, pp. 562-569; letter of November 8, 1833, 

 quoted in F. Danneman, Die JVaturwissenschaften in ihrer Entwick- 

 liing und in ihrem ^usammenhange, Leipzig, 1922, vol. 4, pp. 398— 

 399; letter of November 20, 1833, quoted in E. Feyerabend, 

 op. cit. (footnote 13), pp. 43—46; Gottingische gelehrte Anzeigen, 

 March 7, 1835, vol. 1, pp. 345-357; "Erdmagnetismus and 

 Magnetometer," Jahrbuch fiir 1836 (H. C. Schumacher, ed.), 

 1836, pp. 38-39, 



282 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



