FEENCH STATE TELEGRAPH. 



The other end of this coil-wire is either connected with the line- 

 wire which proceeds to the succeeding station, or with the earth, 

 at the option of the agent, a commutator being provided by which 

 this change of direction may be made. 



185. Let us see, then, in what manner the agent at s, provided 

 with such a commutator, can govern the motion of an indicator at s'. 



The arrangement of the apparatus is such, that when the handle 

 M of the commutator is presented vertically upwards, as represented 

 in the figure, the pin being in the highest notch, the lever L 

 presses against the contact-piece K. 



Let the highest notch be supposed to be numbered 1, and the 

 others proceeding round the disc, in the direction of the motion of 

 the hand of a clock, be numbered successively 2, 3, 4, 5, 6, 7, and 8, 



It must be remembered, that at the other station, s', there is 

 another commutator precisely similar, the corresponding points of 

 which we shall express by the letters M', D', n', &c. 



Let us see, then, how the agent at s, by moving round the 

 handle M from notch to notch, can govern the motion of the indi- 

 cator at s'. 



The commutator and indicator at the station s', when not 

 employed in the transmission of a despatch, are placed respectively 

 with the arm M', having its pin in the notch 1', and the hand of 

 the indicator directed vertically upwards. 



186. The arm M being, as represented in the figure, in the 

 notch 1, let it be moved to the notch 2. The lever L being moved 

 to the right, the piece r will be thrown upon K'. Being then in 

 connection with the battery- wire, the current will pass by r and 

 L to A, and thence by the line-wire to the corresponding point A' 

 of the commutator at the station s', and thence through the pillar 

 to the lever I/ and the piece r'. But since, as has been just 

 explained, M' is in the notch 1', the piece r' must rest against K. 

 The current, therefore, arriving at this point, will pass from- K by 

 the wire to the coil of the electro-magnet at s', to which it will 

 impart magnetism, so that it will attract the armature, and move 

 the anchor of the escapement, so as to make the indicator move 

 from the vertical position 45 in the direction of the hand of a 

 clock. 



If the handle M be now moved from notch 2 to notch 3, the lever 

 L will be thrown back to K, and the contact with K' being broken, 

 the current will be suspended, and the electro-magnet at s' losing 

 its power, the armature will recoil from it by the action of the 

 spring (147) and the anchor of the escapement being again 

 moved, the indicator will be advanced through another angle of 

 45, and will be then in the horizontal position pointing to the 

 right. 



c2 19 



