DEVELOPMENTS IN TELEPHONY AND TELEGRAPHY JEWETT. 503 



TELEGRAPH FOR RAILWAY SERVICE. 



As noted in connection with telephone developments, the produc- 

 tion of suitable selective signaling apparatus has made possible the 

 substitution of the telephone for the telegraph in the handling of 

 train movements on railways. 



As this railway service has been one of the principal uses of the 

 telegraph for more than 50 j^ears, its abolition would appear to make 

 the handling of commercial messages for business not conducted by 

 telephone and the transmission of press dispatches and other matter 

 which can be done most economically in this way the principal future 

 field for land telegraphy. 



SUBMARINE TELEGRAPH CABLE. 



For many years developments in the submarine-telegraph field 

 were practicall}^ confined to improvements in the types of cable em- 

 ployed and to minor improvements in the terminal apparatus. Dur- 

 ing the last fevv^ years there has been renewed activity in this highly 

 important branch of communication. 



In particular much has been done in the way of amplifying the 

 feeble currents received through long ocean cables, thus rendering 

 legible current fluctuations which would otherwise be too feeble to 

 produce readable signals on a siphon recorder tape. A direct result 

 of amplifying the signals has also been increased speed of transmis- 

 sion. 



Within the last two or three years experiments have likewise been 

 made with a view to recording cable signals as dots and dashes on a 

 sounder, so that they can be read by ear, as is done in the case of 

 Morse telegraphs. Just how far this line of development, which 

 would permit connecting together submarine cables and land tele- 

 graph lines, will succeed commercially is a question yet to be de- 

 termined. 



The most recent work on submarine telegraphy has been that of 

 Col. Squier, of the United States xirmy, who has designed a system 

 of alternating-current cable signaling which gives promise of con- 

 siderable application. 



3. RADIOTELEPHONY AND TELEGRAPHY. 



Since the whole life of the art of radiocommunication is scarcely 

 more than 15 years long, everything which has been done is in a 

 sense a recent development. The physical phenomena involved in 

 radiocommunication are so spectacular and weird that more atten- 

 tion on the part of the general public has probably been accorded 

 the progress of the art than is usually given to the commercial de- 



