TELEGRAPHIC INSTRUMENTS. 



transmitting agent has before him a row of keys, like those of a 

 piano-forte (fig. 6), upon which the letters of the alphabet are 



Fig. G. Fromcnt's Alphabetical Telegraph. 



engraved. When he presses down the key upon which any letter 

 is inscribed, the index of the dial at the distant station with 

 which he is in communication turns, and stops when it points at 

 the same letter. In this way, by indicating the successive letters 

 of the words composing the message, the despatch is transmitted. 



The mechanism by which this is accomplished, is fully described 

 in our Tract on the " Electric Telegraph," par. 205. 



Another form of electric telegraph (fig. 7), which writes the 

 message it transmits, may also be seen in operation in M. Froment's 

 workshop. 



The message is transmitted in this instrument by pressing 

 down a key successively by the finger, the key being held down a 

 longer or shorter time, in the same manner as a pianist would 

 play notes of greater or less length. Varying marks of corre- 

 sponding lengths are made upon paper by a pencil at the distant 

 station, the paper being moved under the pencil by suitable 

 mechanism. For a description of this telegraph see also our 

 Tract on the "Electric Telegraph," par. 207. 



14. Another of the results of the mechanical ingenuity of this 

 artist, which may be seen at his workshop, which if not the most 

 useful is assuredly the most astonishing, and to many the most 



205 



