Telegraph

[s. 881] Zell's Condensed Cyclopedia Steinheil's was the first perfect instru Steinheil's was the first perfect instrument invented, and came into operation in July, 1837. It was 12 miles long, and had 3 intermediate stations in circuit. In the same year, and about the same time, Prof. S. F. B. Morse exhibited in the University of New York a T. constructed on the same principle, which had been gradually brought to a working condition by experiments and contrivances derived by the inventor since 1832. This T. was first brought into practical use, May 27, 1844, between Washington and Baltimore. Of the numerous printing and writing T. which have been devised, that of Mr. Morse is the best known, and has been almost universally adopted on the continent of Europe. Every electric T. consists e entially of three parts: 1, a circuit consisting of a metallic connection between two places, and an electro motor for producing the current: 2 a communicator for sending the signals from the one station; and, 3, an indicator for receiving them at the other station. The manner in which these objects, more especially the two last, are effected can be greatly varied, and we shall limit ourselves to a few details on the subject of the working of an electric 7. If the conducting wire which unites the two elements of a galvanic battery be parallel to a magnetic needle before the current is transmitted, the needle will immediately arrange itself at right angles to the wire, when the current is made to pa along the wire. (See ELECTROMAGNETISM.) The effect of the electric current on the needle is doubled, if the conducting wire is bent round so as to pa along the opposite side of the needle; and as these convolutions of the wire are increased in number within certain limits, their effect is also augmented. With such an apparatus, each time the electric current is established and broken, there will be a separate deflection of the needle. As the conducting wire maybe of any length, provided the battery is sufficiently powerful, we have at once a means of communication between distant places and a system of signs suggested: one deflection may mean one thing; two in succe ion another, and so on. But the signals at our disposal are doubled in number if, by reversing the electric current, we cause the deflections to be made in the opposite directions, and their amount is still further increased if we combine deflections in opposite directions. This is in fact the electric telegraph; since all the different forms it a umes are no. more than modifications of it. It is found unnece ary to use two wires - one for the direct current from one place to another, and the other for the return current from the second place back again to the first: the earth answers for one of them. By the recent duplex and quadruplex invention, one wire can be used to transmit several me ages at the same time. It is clear that all the needles in connection with a given wire will be deflected at the same time by the electric current. When, therefore, it is notified for what place the me age is intended, the connection with the other needles at the different stations being cut off, the current is not usele ly retarded. As the telegraph clerk may not be attentive, his notice is attracted by an alarm-bell, set ringing by the electric current. The wires are sometimes carried through the air on poles, insulation being secured by the use of gla or porcelain connections for attaching the wire to these supports; sometimes in tubes underground, insulation being effected by gutta perch a, .; sometimes over the tops of houses, through the sea, . An apparatus with two needles is used at all principal stations: it may be considered as a combination of two simple ones; with it the reading of the signals is more rapid; but it has the inconvenience of requiring two wires. Apparatus has been invented for printing or writing a me age instead of merely indicating it.-Atlantic T. The succe of various attempts to send me ages by electric agency through cables lying under water, for short distances, induced Profe or Morse, of New York, to suggest the po ibility of uniting Great Britain and America by a submarine cable, laid from shore to shore throughout the Atlantic Ocean. In 1845, Mr. J. W. Brett registered an a ociation, under the name of the General Oceanic Telegraph Company, to carry out the object above mentioned, an. to connect England with the continent of Europe in various parts. The latter part of his design was succe fully accomplished in 1851, and public attention, in England, was, in consequence, again directed to the junction of Great Britain and America by similar means of intercommunication. Newfoundland had already been united to the mainland of America by a submarine cable; and in 1856, the Atlantic Telegraph Company was formed, with the design of laying a cable between St. John's, Newfoundland, and Valentia, in Ireland, along the bottom of the Atlantic in its shallowest part, which had been pointed out for the purpose by Captain Maury, and called by him the Telegraphic Plateau. Pecuniary a istance was guaranteed to the company by the respective governments of Great Britain and the United States; and both powers agreed to furnish ships for taking out the cable and placing it in its destined bed. After different attempts made to accomplish this great object, which all terminated without practical result, the cable was at last succe fully laid, when, on the 5th of August, 1866, it broke, abt. 88 m. from Heart's Content, in Newfoundland. Nothing daunted, the operators in this mighty scheme again set to work for the fourth time, and on the 28th July, 1867, the telegraphic junction was at last succe fully achieved, and came into practical busine use, as it has since remained. In addition, the last expedition recovered the lost cable of 1866; which has also since been brought into active operation. In July, 1869, a third cable acro the Atlantic, called the French Atlantic Cable, was laid from the port of Brest, in France, to Saint Pierre, in America. The form of these cables is much the same. The copper conductor consists of seven wires (gauge No. 18), weighing 800 lbs. per nautical mile. These are made into a single strand, and are imbedded in a pitchy mixture called Chatter ton's Compound. Over this are laid four layers of gutta perch a alternately with three of Chatter ton's compound, the diameter of the core thus formed being 0.464 inches. The object of using so many coatings is, that if an air-bubble should occur in any one of them, the great pre ure to which the cable is exposed may not be able to force water completely through to the conducting-wire, and thus to effect the destruction of the insulation. The external protection consists of ten solid wires (No. 13 gauge), surrounded separately by Manilla yarn, which has been saturated with a preservative compound, and these are laid spirally round the core previously padded with hemp. The weight in air is 35 cwt. 3 qrs., and in water 14 cwt. per knot; and the breaking strain is 7 tons 15 cwt. - that is, the cable would bear 11 nautical miles of itself suspended in water. The deepest water was 2,400 fathoms. The reader who desires more information will find it in the following works: The Electric Telegraph; its History and Progre , by E. Highton (London, 1854); The Electro-Magnetic Telegraph, by L. Turn bull (Philad.. 1853); The History of the Electric T., by G. B. Pre scott (Boston, 1866); The Atlantic T., by Dr. W. H. Ru ell (Lond. 1866); The Electric T., G. B. Pre scott (N. Y.1877). [s. 882]