no 



NATURE 



\yttne lo, 1875 



THE PROGRESS OF THE TELEGRAPH * 

 VII. 



IN 1 843 Alexander Bain made certain important improve- 

 ments in the recording and transmitting instrument 

 shown in Fig, 28, in which two semicircular magnets B B', 

 with similar poles facing, fixed to a brass bar, move through 

 the centres of two coils, A a', the index-hand pointing 

 to I or V according to the direction of the current. This 

 was controlled by the metallic contacts N n' n" n'" open- 

 ing or closing the battery and line circuits according to 

 the position of the handle F. The connection and direc- 

 tion of the current through the instrument from the bat- 

 tery D is indicated by the arrows, the connection R being 

 that of the line wire, and S that of the earth circuit. 



This patent and certain others that will be brought 

 under notice gave rise to expensive litigation in the 

 early history of the telegraph. In 1846 John Nott 

 produced his letter-recording telegraph, which, in con- 

 junction with Mr. Alexander Bain's inventions, was 

 carried into the law courts on a question of infringement 

 of the Cooke and Wheatstone patent rights ; but for 

 reasons already given regarding patent law, the oppo- 

 sition was unsuccessful on the part of the Electric Tele- 

 graph Company. 



contact drums,/,/, which regulated the direction of the bat- 

 tery current through the electro-magnets, by means of the 

 index shown in the external view (Fig. 29) being moved 

 to the one side or the other. 



ain's I and V telegraph, 1843. 



Nott's apparatus is shown in external and internal eleva- 

 tion in Figs. 29 and 30. It consisted of a dial showing 

 the letters of the alphabet and numerals repeated four 

 times in the circumference of the circle. The respective 

 letters or numerals were indicated by the step-by-step 

 motion of a revolving pointer or index-hand. The motion 

 of this pointer was controlled by successive make-and- 

 break contacts with the battery by means of a finger-key 

 dipping into a mercury cell, d. The index-pointer was 

 driven round by a " clawker- and- driver " action in con- 

 nection with the toothed wheel c, the propelling power 

 being derived from the attractive and repellant action of 

 two horseshoe electro-magnets, a, d, acting upon soft iron 

 armatures in connection with the '" clawker-and-driver " 

 motion. The electro-magnet b governed the alarum or 

 call- signal. Either the speaking or alarum portion of the 

 telegraph was brought into action by the position of the 



* Continued from p. 72. 



In 1846 High ton's gold leaf indicator was brought under 

 notice, and an important automatic chemical printer- 

 recording high-speed telegraph, by Alexander Bain, which 

 has been the germ of several of the applications in the 

 modern high-speed automatic arrangements (Fig. 25). In 

 this chemical printer, a paper strip, perforated with holes in 

 symbolic groups to represent the several words of the mes- 



FiG. 30. — Nott and Gamble's patent, 1846. Internal arrangement. 



sage, was employed to regulate the automatic sequences of 

 the current through the line. This paper ribbon was passed 

 over a metal drum in circuit with the line wire, and a fine 

 metal style in connection with one pole of the battery 



