Merchant, F. W. (Francis Walter), 1855-1937, Chant, Clarence Augustus, 1865-1956 · Toronto : Copp Clark · leaf 437
516.-Magnetdc field of currents in OppOsitc directions (Fig. 516).in opposite directions. 506. Practical Applications of the Magnetic EflFects of theCurrent. No sooner were the principles of electromagnetismmade known by the researches of the early investigators thantheir practical applications… … THE ELECTRIC TELEGRAPH—TELEGRAPH KEY 427 Ampere, in 1821, suggested the possibility of transmittingsignals by electioniagnetic action. Joseph Henry used anelectromagnet at Albany, in 1831, for producing audible signals.In 1837, Morse devised the system by which dots and dashes,representing letters…
Physics
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