CHAP, iv.] ELECTRIC TELEGRAPHY. 591 



accomplished by means of a conical pendulum regulator or a vibrating 

 plate. 



The apparatus being regulated, the sending clerk makes the letters 

 composing the message by depressing the keys in succession, and it 

 is printed simultaneously at the two stations. 



. We see, by this rather long description, though we have omitted 

 certain mechanical details, that Hughes's printing telegraph is con- 

 siderably more complicated than those before described. But this 

 complication, necessitated by the many difficulties of the problem to 

 be solved, only serves to make the result obtained more admirable, a 

 result really marvellous, when it is remembered that the rapidity of 

 transmission is three or four times that of Morse's. While with the 

 latter twelve to fifteen words on an average cari"*be sent per 'minute, 

 Hughes will print thirty or forty in the same time. 



Ingenious in mechanism and mechanical detail as the Hughes type 

 printer undoubtedly is, in practice it is not found to be reliable in 

 a variable climate ; the loss of insulation from partial rains and other 

 atmospheric changes over a long line, entail such delicate adjustments 

 to secure the synchronism of the sending and receiving instruments 

 that the loss of time from such adjustments is not compensated 

 sufficiently by any mechanical instrumental capabilities, and the 

 Hughes printer has more or less given place to the Wheatstone 

 automatic transmitter. 



III. WHEATSTONE'S AUTOMATIC HIGH-SPEED PRINTING TELEGRAPH. 



In his automatic apparatus Whentstone has employed a similar 

 principle to that of the Jacquard loom, that is, he weaves his 

 currents rapidly into the line by the previous preparation of an 

 electrical card, having the necessary sequence of currents to form the 

 letters and words composing the message in readiness before it is 

 placed upon the instrument, by which the time occupied in transmit- 

 ting any number of currents and groups of symbols to represent letters 

 and words is reduced to a minimum, and the delay and cost incident 

 to manual labour in the direct transmission of the message over the 

 wire are avoided. One of the chief problems of mechanical telegraphy 

 is to obtain the greatest amount of speed out of a wire in a given 



