Gauss and !Veber transmitting- apparatus in the Gauss and Weber system was a magnetic needle enclosed in a coil of wire, and the currents were produced by a magneto-electric inductor. The receiv ing apparatus (pi. 58, fig. 1) was a large coil, or " multiplier," of insu lated copper wire, the ends of which were connected with the line wires. Within the multiplier was suspended by a fibre of silk a permanent mag net, to whose spindle a long" mirror was attached in such a manner that it would throw into the axis of a telescope suitably mounted at a distance of ro or 12 feet the reflected image of a horizontally-divided scale. A system of right- and left-hand deflections of greater or less amplitude on the narrow scale constituted the alphabet. The movements of the inductor at the transmitting- station caused the transmission of currents through the line wire, which affected the magnetic needle within the multiplier and became manifest by slight movements of the magnet. These slight movements were greatly multiplied by the action of the mirror and the telescope. An apparatus similar to this in principle is used at the present time in subma rine-cable telegraphy. (See p. 35r.) Sleinheil' s of Munich substantially improved the magneto-electric teleg.,raph of Gauss and Weber, both in the construction of the induction apparatus for g-enerating the magneto-electric currents and in the receiving apparatus. The latter (N. 5S, Jig. 3) was composed of two needles or bars within a multiplier and having their free adjacent ends prolong-ed to terminate in a species of pen, which imprinted a series of dots upon the surface of a strip of paper that was caused to travel past them. To Steinheil also is accorded the credit of having made the very important discovery that the second, or return, wire of a telegraphic cir cuit was unnecessary, and that by simply grounding the wires at the ter minal station the return current would pass through the earth. While Gauss and Weber, and Steinheil, employed the magneto-electric current in their telegraphs, Wheatstone and Cooke in England returned to the use of the voltaic current, which is better adapted to the purpose, and in 1837 the latter patented certain improvements upon Steinheil's needle telegraph.
First .1Iorse Tek.Traph.-111 1835, AIorse in the United States con structed the first crude working model of his well-known electro-magnetic telegraph ( jig. 4), which embodied the following parts—namely, " a sin gle circuit of conductors from some suitable generator of electricity; a system of signs, consistinp,- of dots or points, and spaces to represent numerals; a method of causing the electricity- to mark or imprint these signs upon a strip or ribbon of paper by the mechanical action of an elec tro-magnet operating upon the paper by means of a lever armed at one end with a pen or pencil; and a method of moving- the paper ribbon at a uni form rate, by means of clock-work, to receive the characters." Fig ure 7 represents the modified form of the register or recording instru ment used by Morse on the first experimental line between Washington and Baltimore, opened on the 27th of AIay, 1844. The arrangement of the circuits is shown in Figure 5. Figure 8 exhibits a register of more modern design, embodying, however, the same elements of construction.
Re/ays.—Of much importance at this stage of the art was the introduc tion by Wheatstone of the so-called " relays," by which the line current is relieved of the work of making the signs that constitute the message, but is caused to generate strong local currents which are employed to actuate the recording mechanism. The relay is shown in Figure 34 (pi. 57). Its object is to call into action the power of a local battery by which the work of recording is performed. This is necessary for the reason that the cir cuit current is too feeble to do more than establish a communication with the local battery. It consists, as will be observed by an inspection of the Figure, of an electro-magnet, M, AI, whose iron armature is attached to the pivoted lever, 13, B'. The back end of the lever is drawn down bv the spring, f, and the armature by this means is separated from the magnet poles, :NI, M. The front end of the lever rests either against the insulating- ivory point of the thumb-screw, D, or against the conducting steel point of the screw, D', according as the current entering through the wire conductor, passing through the coils of the electro-magnet, M, and then to the earth, causes the armature, A, to be attracted to the poles of the magnet, or, as the current ceases to flow, the retractile power of the spring, f, collies into play. The brass standards, E, C, S, are insulated from the base board, P, P'. L, K is the local lattery which is thrown in or out of circuit by the relay. R is the receiving instrument. It will be apparent from the foregoing description that when the main, or primary, circuit energizes the magnet, MAI, and causes its armature to be attracted, thus making contact between B and D', the local battery will be closed, its current proceeding from K to the receiving instrument, and from this back to the battery. The relay employed on the closed-circuit lines differs from that of the open-circuit line just described simply in the reversed arrange ment of the points B, B'. (Comp..p/. 57, fig. 35.) At present the source of the electric current almost universally employed in telegraphy is a voltaic battery.
The Batteries in most general nse for telegraphic purposes are the fol lowing: the Meidinger cell, composed of zinc and copper elements in a cell without porous cup, the two liquids constituting- the electrolyte being kept apart simply by the difference of their specific gravities (the liquids employed are solutions of sulphate of copper and sulphate of magnesia, a reserve supply of crystals of sulphate of copper being provided in some convenient manner, so as to make good the consumption of this salt by the action of the battery); the Marie-Davy cell, composed of zinc-carbon ele ments, in which the carbon is immersed in a paste of moistened sulphate of mercury and the zinc in pure water; the Leclanche cell, of zinc-carbon elements, in which the carbon plate is placed in a porous cup filled up with frag-ments of peroxide of manganese and carbon and the zinc occupies the outer vessel, and in which a diluted solution of sal-ammoniac consti tutes the electrolyte. The qualities sought for in a battery are that it shall furnish a current of great constancy and shall require the least pos sible attention for cleansing.