CHAP, iv.] ELECTRIC TELEGRAPHY. 603 



which the tracer starts, and the other two marking the limits of the 

 message. 



Nothing is simpler, now, chan the working of the pantelegraph. 

 The message, when written, is placed on the surface of the trans- 

 mitting cylinder. The clerk makes the warning signals (by alarums 

 or otherwise), and then sets the pendulum going. The transmission 

 of the message is accomplished automatically, without the clerk 

 having any work to do, and consequently without being obliged to 

 acquire any special knowledge. Since two dispatches may be sent at 

 the same time and since shorthand may be used the rapidity 

 of transmission may be considerable. "The long pendulums of 

 Caselli's telegraph," says M. Quet, 1 "generally perform about forty 

 oscillations a minute, and the styles trace forty broken lines, separated 

 from each other by one-third of a millimetre. In one minute the 

 extreme lines described by the styles are separated from each other 

 by 13 millimetres and in twenty minutes by 260 millimetres. As we 

 can give the lines a length of 11 centimetres, it follows that in twenty 

 minutes Caselli's apparatus furnishes the facsimile of the writing, 

 poi traits, or drawings traced on a metallized plate 11 centimetres broad 

 by 26 centimetres long. For clearness of reproduction, the original 

 writing must be very legible and in large characters." 



Since 1865 the line from Paris to Lyons and Marseilles has been 

 open to the public for the transmission of messages by this truly 

 marvellous system. 



A clerk in the French telegraph service M. Meyer has invented 

 and constructed an autographic telegraph on a different principle 

 to the Caselli pantelegraph, but which also works with remark- 

 able regularity and rapidity, and reproduces the messages sent in 

 facsimile. 



The transmitter of Meyer's pantelegraph (Fig. 392) is a cylinder, 

 round which is rolled the message, written in the same way as in 

 Caselli's system. This cylinder receives a uniform motion from 

 clockwork, regulated by a vibrating plate. A metallic style, carried 

 on a little rail, moves in the direction of the axis of the cylinder, on 

 the surface of which it describes a helix or spiral of very low angle. 

 It is connected with the battery and the line- wire, and in consequence 

 it closes or opens the circuit between the two stations in correspond- 

 ence, according as it encounters, on the metallized paper of the 

 1 Ihipport sur les progres de Celcctricite et du Htaynetisme. 



