THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



AL OF SCIENCE. 



^ &0 Jfy L s ^™ SERIES.] 



LXXXII. On a Dynamo for maintaining Electrical Vibrations 

 of High Frequency. With some notes on the Transmission of 

 Waves in Wireless Telegraphy. By Sir Oliver Lodge *. 



I DESIRE not so much to put on record, since that has 

 in some sort been already done, but to welcome the 

 achievement of what many physicists in years past desired to 

 attain, namely the construction of an alternating arrangement 

 capable of maintaining electrical vibrations of sufficiently high 

 frequency to give a continuous train of waves of moderate 

 length ; comparable for instance to four miles or even less. 

 It may be that this problem will give way, as problems so 

 often do, in several directions at once ; and that the result 

 may be — possibly has been — achieved by several different 

 methods. At present, however, my attention has been called 

 to the ingenious device introduced by Dr. Groldschmidt of 

 Berlin, an ex-Professor of Electrotechnics at Darmstadt. 



A method of achieving the desired end by a series of 

 alternating dynamos had already been suggested, and will be 

 found referred to in Professor Gr. F. FitzGre raid's Collected 

 Papers, page 280, where a discussion between himself and 

 Dr. Sumpner, involving also Professor Trouton, is reported 

 as having occurred at the Physical Society of London on 

 22nd January, 1892; with myself, as it happened, in the chair. 

 It is reported also in Nature, vol. xlv. p. 358. 



The plan then mooted was to use the alternating current 

 from one dynamo to excite the field magnets of another, that 



* Communicated by the Author. 

 Phil Mag. S. 6. Yol. 25. No. 150. June 1913. 3 F 



