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Recent Advances in Telegraphy. 
[July 
Ten years later, in 1870, Mr. Cromwell Fleetwood Varley, 
F.R.S., appears to have first clearly designed the employ- 
ment of the telephone in the transmission of several mes- 
sages simultaneously on one line wire, by means of separate 
notes. Varley’s patent of that year is full of most ingenious 
plans and contrivances, not only for the sending and re- 
ceiving of telephone messages, but for rendering the vibratory 
eledtric signals visible, both temporarily, by light, and per- 
manently, by recorded marks on moving paper. The prin- 
ciples of later inventions are to be found here, and even 
some of the details. But Varley seems to have left the 
carrying out of his system in abeyance; and the merit of 
practical success belongs to the systems of M. Paul la Cour, 
of Copenhagen, and Mr. Elisha Gray, of Chicago. 
The principle of all these systems is that a vibrating body, 
such as a tuning-fork or membrane, emitting a certain note, 
shall be caused at each vibration to interrupt an eledtric 
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current in the telegraph line ; and the current so interrupted 
shall, at the distant station, be made to set a corresponding 
body in vibration, so as to reproduce the original note there. 
Of course it is possible, by having a number of vibrators at 
the sending station and a corresponding number of vibrators 
in unison with them at the receiving station, to give rise 
simultaneously to several distindt sets of eledtric vibrations 
in the line wire, and to reproduce several distindt notes at 
the receiving station. In this way is multiplex transmission 
rendered feasible. 
M. Paul la Cour’s English patents bear date 1874 and 
1876. Briefly, his system is as follows : — Fig. 11 represents 
his sending arrangement. F is a tuning-fork which is put 
into vibration, and makes contadt once every vibration with 
the contadt-point p. The fork is connected, through the 
signalling-key, with the sending-battery, and the contadt - 
point P is connected to the line. Here the fork is simply 
shown, and must be started by hand ; but in his later patent 
