Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ion of thetelegraph. 312. vYe come now to the electro-magnetic tele^graph, which, in its beautiful simplicity and efficien-cy, surpasses all others yet introduced into practice ELECTRO —MAGNETIC TELEGRAPH. 195 Barlow, in England, seems to have made some earlysuggestion of this kind; but it was not until 1830,on the construction of the first powerful electro-magnets, by Professor Henry, of Princeton, N. J.,that this form of telegraph became possible ;
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . ion of thetelegraph. 312. vYe come now to the electro-magnetic tele^graph, which, in its beautiful simplicity and efficien-cy, surpasses all others yet introduced into practice ELECTRO —MAGNETIC TELEGRAPH. 195 Barlow, in England, seems to have made some earlysuggestion of this kind; but it was not until 1830,on the construction of the first powerful electro-magnets, by Professor Henry, of Princeton, N. J.,that this form of telegraph became possible ; and inhis first paper on the results of these experiments,in some of which long wires were used, he at onceapplies the new facts to the telegraph. The pres-ent form of the American telegraph is claimed tohave been suggested in 1832, by Dr. C. T. Jackson,and by Professor Morse. It was finally matured byProfessor Morse, and introduced by him betweenBaltimore and Washington, in 1844, after a delaybefore Congress of more than six years. 313. Electro-magnetic Telegraph. — Pig. 133represents the recording part of the telegraph. It Fig. consists of an electro-magnet, armature, and lever,arranged in a similar manner to the magnetometer,(Fig. 131.) At the extremity of the lever is a bluntpoint, which marks the strip of paper when the elec-tro-magnet is in action. If one wire from the batteryis placed in one of the screw-cups, whenever theother wire is touched to the remaining cup, the arma- 196 Daviss manual. ture is powerfully attracted by the magi et, and thepoint on the lever presses the paper into the corre-sponding groove of the roller, so that lines or dots artmade according to the time during which the contactwith the battery is maintained, the paper being slowlydrawn under the roller. 314. The following table exhibits the signs em-ployed by Professor Morse : — MORSES TELEGRAPHIC ALPHABET. ALPHABET. a c - - - d e - g h i - -I m n 0 - - P q r - - - s t — u w X - - y
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
