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Recent Advances in Telegraphy. [J uly, 
Muirhead’s system was first experimentally tried, by Dr. 
Muirhead and the writer, on the Marseilles to Bona (Algeria) 
cable of the Eastern Telegraph Company, in 1875. The 
following year it was established for the regular traffic on 
the Marseilles to Malta section, and on the Suez to Aden or 
Red Sea cable, which is 1460 miles long, and in an electrical 
sense one of the longest of existing cables. Early in this 
year it was established on the Aden to Bombay section, a 
cable of 1817 miles long. There are thus upwards of 
4000 miles of this Company’s lines to India worked on the 
duplex system, and it has been given out that the Company 
hopes this year to apply it to ail their cables. 
The duplex system of transmission is without doubt a 
great practical gain, since it doubles the carrying capacity 
of a line, and makes it speak, as it were, with two tongues. 
With such faCts as the above before us we can no longer 
regard it as a “ species of intellectual gymnastics.” It has 
been brought at last to a serviceable issue, and bids fair to 
become a considerable public benefit. 
Quadruplex Telegraphy. 
Very soon after Dr. Gintl, by his invention of the duplex 
system, had shown the feasibility of simultaneously transmit- 
ting two messages counter to each other along one wire, 
electricians engaged their minds with the allied problem of 
transmitting two messages simultaneously in the same di- 
rection. And they were not backward in foreseeing that by 
the union of both methods a system of quadruplex tele- 
graphy would be placed in their hands. On the 27th of 
October, 1855, Dr. J. Bosscha, jun., of Leyden, at a meeting 
of the Royal Academy of Sciences, Holland, described a 
method he had invented for the simultaneous sending of two 
messages in one direction along one wire, and likewise 
pointed out that, by the union with it of the Frischen-Siemens 
duplex system, a means of sending four messages simulta- 
neously was provided. On the 31st of the same month Dr. 
J. B. Stark, of Vienna, published his method of double- 
sending in the same direction, and concluded his account as 
follows : — “ With the method of double transmission in the 
same direction we may also combine that of counter-trans- 
mission (gegensprechen), and hence arises the possibility of 
simultaneously exchanging four messages upon one wire be- 
tween two stations, which will, however, hardly find any 
application in practice.” 
