512 Mr. W. Duddell [May 17, 



kilowatts high frequency energy is generally sufficient for practical 

 purposes at the higher frequencies. At the lower frequencies, which 

 are mainly used on long-distance working, large amounts of power are 

 required. In fact one of the great problems in long-distance wireless 

 telegraphy is to produce several hundred kilowatts of high frequency 

 energy with certainty and regularity, and at a reasonable price. 



The relative advantages of high frequency alternating current, 

 sometimes called continuous oscillations and groups of oscillations, is 

 not a matter that I can enter into to-night. It is sufficient to point 

 out that if continuous oscillations are employed they can always be 

 cut up into groups by means of an automatic device should tliis be 

 required. Neglecting the relative advantages of the continuous 

 oscillations and the oscillations which are sent out in groups with 

 spaces between, I have simply to compare the three methods from 

 the point of view of the amount of energy they are able to successfully 

 and regularly handle. 



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Fig. 18. — Connections foe S. G. Brown's Wheel. 



The alternator method, as far as the information at my disposal 

 goes, has never yet been applied to very large powers. There is no 

 doubt that it is from many points of view an ideal method. 



The spark method has been successfully employed over a wide 

 range of frequency and up to very large powers, and there is no 

 doubt that it is capable of satisfactory operation. The spark method 

 used with very high frequency sparks and continuous current, as 

 proposed by Mr. Galletti, is still in its experimental stage. With 

 the rough apparatus I saw working a year ago, a considerable amount 

 of power could be dealt with successfully, and there seems no reason 

 why the principle should not be extended so as to deal with still 

 larger powers. The practical difficulties may be great, but I think 

 they should be able to be overcome. This, however, is entirely a 

 matter for experiment. 



The arc method is in a much more advanced condition. A large 

 amount of work has been done, and practically all the details have 

 been worked out. There is no doubt that fairly large powers can be 

 successfully generated and utilized. 



