1907.] on Recent Contributions to Electric Wave Telegraphy. 



695 



continuous trains of electric waves will doubtless greatly assist space 

 telegraphy, it does not follow that their generation by the arc method 

 is the best or final method. 



In the production of continuous oscillations we are not limited to 

 the arc method. Mr. Marconi has for some time past been engaged 

 in developing an ingenious method of creating undamped electric 

 waves for telegraphic purposes which involves neither an arc nor 

 alternator, but is a new mechanical method of great simplicity. 



This method is capable of producing astonishingly large alter- 

 nating currents of very high frequency, in other words, so called 

 undamped or persistent oscillations. I have recently witnessed some 

 of his experiments, and was surprised at the results obtained. Long 

 distances have been telegraphically covered with every prospect of 

 great efficiency. Unfortunately, the incomplete state of certain 



Fig. 12. — Electrolytic Detector. 



foreign patents prevents me from entering into details of this method 

 now, but I hope he himself will be able to do so soon. Turning 

 then from transmitters to receivers, we may notice one or two recent 

 types. By far the larger portion of electric wave telegraphy was 

 until a few years ago conducted by means of some form of coherer, 

 either requiring tapping or else self -restoring. The coherer in certain 

 forms has the advantage that a current of about O'l to I'O milliam- 

 pere can be passed through it, and hence through a relay, so that 

 messages can be printed down by it when using a Morse inker in dot 

 and dash signals. After that came Mr. Marconi's magnetic detector, 

 making use of a telephone to create an audible signal. This is now 

 the instrument employed by him on all long distance work. In 

 G-ermany and the United States a type of telegraphic wave detector 



