. Bulletin. Science. ./"..... RAUNSCHWEIG •wOLFEHBUTTtL GEHTHIN * riAue HALBERSIADI ^BRANDENBURG MAGDEBURG COBLENZ Figure 4.—Map of the German semaphore telegraph system between Beriin and Coblenz during the 1830's. Adapted from Archivjuer Post unci Telegraphle, 1888, vol. 16, p. 230. recognize the theoretical basis for such a transmission; that is, that the current in a simple closed circuit has the same value at every point in the circuit. Ampere originally believed that each conductor in a circuit— each of the loops of wire in a coil, for example— required its own chemical cell. Pierre
. Bulletin. Science. ./"..... RAUNSCHWEIG •wOLFEHBUTTtL GEHTHIN * riAue HALBERSIADI ^BRANDENBURG MAGDEBURG COBLENZ Figure 4.—Map of the German semaphore telegraph system between Beriin and Coblenz during the 1830's. Adapted from Archivjuer Post unci Telegraphle, 1888, vol. 16, p. 230. recognize the theoretical basis for such a transmission; that is, that the current in a simple closed circuit has the same value at every point in the circuit. Ampere originally believed that each conductor in a circuit— each of the loops of wire in a coil, for example— required its own chemical cell. Pierre Simon Laplace pointed out to Ampere that the Oersted effect could be produced everywhere in a long conductor, which fact argued for the hypothesis that the galvanic current was everywhere the same. Accordingly, a magnetic needle would be able to indicate the pres- ence of a current when a battery was connected to a wire through which the current was passed, no matter how long the wire or how far away the needle. By using a pair of wires and a magnetic needle for each letter of the alphabet, Ampere suggested that one could communicate at a distance by opening and clos- ing the circuit proper to each letter, for the motion of the needle would indicate the appropriate symbol. William Alexander' demonstrated at an exhibit in Edinburgh in 1837 how such an Amperian needle telegraph might be set up (fig. 8). The distance covered by this exhibit was only 5 feet, but the ex- hibit showed how 30 wires and a copper rod, which was used for the common return, could indicate all the letters of the alphabet and some of the punctua- tion marks. When the battery was connected to a certain wire, the closing of the circuit caused the mag- netic needle associated with that wire to move and to uncover the corresponding letter of the alphabet on a panel. The combinations obtained by closing the circuits in proper order resulted in the transmissions of combinations of the letters that formed
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Keywords: ., bookauthorunitedstatesdepto, bookcentury1900, booksubjectscience
