TECHNOLOGY. 587 



will doubtless be vastly extended. Sir Henry Thompson, 

 and others following him, have successfully applied it in sur- 

 gical operations and in medical examinations ; Rosetti has 

 employed it in the detection and observation of obscure seis- 

 mic phenomena; and Houston and Thomson have applied it 

 as a relay for the telephone. The utility of the telephone 

 likewise has manifested itself in its extensive introduction 

 into practical use ; and we may note, as one of the most use- 

 ful developments during the past year, the establishment of 

 a system of telephone exchanges, by which a number of per- 

 sons, who subscribe for the purpose, are brought into commu- 

 nication with each other through the medium of a central 

 station. 



The past year also witnessed the practical solution of the 

 problem of duplexing submarine cables, by which their ca- 

 pacity for transmission has been materially increased; Muir- 

 head's duplex system having been applied to the Madras- 

 Penang section of the Eastern Telegraph Company's lines, 

 and to that of the French Atlantic Cable, and Stearns hav- 

 ing duplexed one of the Anglo-American lines. The quad- 

 ruplex system, which was first introduced upon the postal 

 telegraph system of England, in 1877, is reported to have 

 proved so successful that it has been introduced upon addi- 

 tional circuits. 



The gradual completion of the extensive net-work of un- 

 derground cables, for some time in course of construction 

 in Germany, to connect the principal cities of that empire, 

 argues well for the success of the system in general. The 

 latest information we have on this point gives the under- 

 ground cable lines in Germany an extent of 2044 kilometers 

 (1267.28 miles), in the following divisions: 1. Berlin, Halle, 

 Frankfort-on-the-Main, with the branch lines, Halle -Leipsic 

 and Frankfort-on-the-Main - Strasburg ; 2. Berlin, Potsdam, 

 Magdeburg, Cologne ; with Cologne, Elberfeld, Bremen ; and 

 3. Berlin, Hamburg, Kiel. The underground lines already 

 laid are reported to give the utmost satisfaction ; and the en- 

 tire length of the lines that have been decided upon, and 

 which are either at present in course of construction or will 

 be shortly completed, is 16,121 kilometers (9995.02 miles). 

 In this country the underground system even in the cities, 

 where their use is almost universal abroad does not appear 



