Page:The American Cyclopædia (1879) Volume XV.djvu/639

 TELEGRAPH 611 another, and thus two letters were indicated. Sommering found that the addition of 2,000 ft. of wire produced little or no sensible addi- tional resistance, and that voltaic action was instantaneously developed at least for the dis- tance of 3,000ft. In 1810 Prof. Coxe of Penn- sylvania suggested a method of telegraphing by means of the chemical effect of electricity, weigger described an improvement upon mmering's arrangement, by which all the res could be dispensed with except two. The ries then known were insufficient for the ission of currents through great dis- ces, and besides were deficient in sustain- ing power; therefore no further progress was ~.e in perfecting the electric telegraph until e principles of electro-magnetism had been .eveloped. (See ELECTRO-MAGNETISM.) In 1819 Oersted discovered the power which the cur- rent possesses of deflecting a magnetized nee- dle out of the magnetic meridian. In 1820 Schweigger added the multiplier. This was followed by Arago's discovery in the same that a steel rod was magnetized when laced across a wire which was carrying a rrent. Ampdre immediately substituted a lix for a straight wire. In 1825 Sturgeon soft iron in place of steel, and the electro- magnet was born. Between 1828 and 1830 Prof. Henry of Princeton, N. J., made great improvements in the construction of electro- magnets by covering the wire and winding the coil compactly. In 1831 he devised an instru- ment which is essentially the same as the Morse register. Moreover, Ohm in 1827, and Fechner in 1831, published the results of their theoretical investigations into the laws of the voltaic current, which shed a flood of light on the subject of telegraphing at long distances. If these investigations had but little practical effect, it was because they were not generally known until the same results had been at a later day worked out empirically. Equally important was the invention of the constant battery by Daniell in 1836, and of various other constant batteries which have been con- trived since that time. The discovery of mag- neto-electricity by Faraday in 1831, and the introduction at a much later date of the induc- tion coil, supplied constant sources of intense electricity adapted to the telegraph. Within a year after Oersted's discovery Ampere pointed out its applicability to telegraphic signals. His plan contemplated at least 30 needles and 60 independent wires. In 1828 Ritchie gave an experimental illustration of such a device before the royal institution of London. In 1829 Fechner had a similar project for uniting Leipsic and Dresden by means of 24 sets of underground wires. In 1832 Schilling ex- hibited to the emperor Nicholas of Russia a needle telegraph in operation on a small scale. He used a needle provided with a multiplier of insulated wire for each letter or number to be indicated. The several wires were brought to- gether beyond the multipliers into one cord, and thence passed to the first station. Eventu- ally he succeeded in reducing the number of needles to one. He also introduced an alarum at the commencement of the passage of the current by causing a solid body to fall, on the same principle as had been "already recom- mended by Prof. Henry in his lectures. These experiments were interrupted by his death, and the steps made were lost, without even a very accurate account of the results being pre- served. The next experiments of importance were those of Gauss and Weber of Gottingen in 1833 and 1834. They employed first voltaic electricity excited by numerous small elements, and afterward a magneto-electric machine to transmit signals from 9,000 to 15,000 ft. They caused a magnetic bar to be deflected to one side or the other, and interpreted its repeated movements into the letters of the alphabet. The vibrations of the magnet were checked by a damper, or by the use of currents alternating in direction. This telegraph was of practical value in comparing clocks and for other pur- poses. Gauss stimulated his pupil Steinheil to a bolder undertaking, in which he was as- sisted by the Bavarian government. Stein- heil's telegraph, completed in 1837, extend- ed 12 m., employed but a single wire, and made use of the earth to complete the circuit. The signals were sounds produced upon a series of bells of different tones, which soon became intelligible to a cultivated ear ; and the same deflections of the needle that caused the sounds were also made to trace with ink lines and dots upon a ribbon of paper moved at a uniform rate, the alphabet having a remote resemblance to that invented by Swaim in 1829. Steinheil used a magneto-electric machine, but with the magnets stationary and the multiplying coils revolving close to them. Morse's telegraph, which is generally recognized in all parts of the world as the most efficient and simple, was first publicly exhibited in the university of New York in 1837. It had been gradually- brought to a working condition .by experi- ments and contrivances devised by the inventor since 1832, with the assistance of L. D. Gale and George and Alfred Vail. In October, 1837, Prof. Morse filed a caveat in the patent office to secure his invention ; and he obtained the patent in 1840, covering the improvements he had in the mean time made in the apparatus. The telegraph was first brought into practical use, May 27, 1844, between Washington and Baltimore. An insulated wire buried in a lead pipe underground was first tried, and failing was replaced with one on posts. The power was derived from a voltaic battery, and an electro- magnet was employed at the receiving station for developing its effects. When the current flowed, this magnet attracted an armature, by which, according to the duration of the cur- rent, dots or lines were marked upon a moving slip of paper with a pen or pencil. The appa- ratus furnished a simple and effective means of recording signals, which by the needle tele-