CHAP, iv.] ELECTRIC TELEGRAPHY. 577 



currents thrown into the line by the sender, magnetizes and demag- 

 netizes the soft iron of the electro-magnet in the same order, and with 

 the same alternations and for the same duration as the signals of the 

 manipulator. The soft iron armature of the indicator in the form of a 

 lever, is attracted and then drawn back into its position by an opposing 

 spring or repelled when the current ceases. This lever oscillates 

 about a horizontal axis and is limited in its oscillations by two screws. 

 The end of it away from the poles of the electro-magnet carries a 

 point which presses against a band of paper, and leaves there a 

 discontinuous mark whose length is proportional to the duration of 

 the current. The intervals between these marks are on the contrary 



,_ mm FK;. 373. Indicator of the Morse telegraph. 



so much the longer, as the continued interruption of the current is 

 greater. A clockwork arrangement, which can be put in motion at 

 pleasure by means of a catch, continuously unrolls some paper that is 

 rolled upon a cylinder, and rolls it on to two other cylinders as soon as 

 the style has described upon it the series of marks which constitute 

 the message. 



At first, the lever of the indicator was provided with a pencil, 

 the point of which traced the marks on the paper, but the point soon 

 wore down arid for that reason the inventor has substituted for the 

 mark of a lead pencil the scratching produced by a metallic point. 

 But in truth this latter method requires a force that the current of the 



p P 



