THE 



LONDON, EDINBURaH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



APRIL 1889. 



XXXIV. On Rays of Electric Force. 

 By Prof. Dr. H. Hertz*. 



AFTER I had succeeded in showing that an electric oscil- 

 lation could give rise to a wave capable of radiating 

 into space, I at once made the attempt to intensify this effect 

 and to make it sensible at greater distances by placing the 

 exciting conductor in the focus of a large paraboKc mirror. 

 These attempts did not succeed, and I convinced myself that 

 the failure w^as the necessary result of the wrong proportion 

 existing between the length of the waves employed, viz. 4 to 

 5 metres, and the dimensions of the mirror in the most favour- 

 able case possible. I have lately observed that the experiments 

 described by me can quite well be performed with oscillations 

 more than ten times as rapid, and with waves more than ten 

 times as short as those at first discovered. I have therefore 

 returned to the use of concave mirrors, and have attained 

 better results than I had ventured to expect. I have suc- 

 ceeded in producing distinct rays of electric force, and in 

 performing with tliem the elementary experiments which one 

 is accustomed to perform with hght and with radiant heat. 

 An account is here given of these experiments. 



The Apparatus. 



The method of producing short waves is the same as that 

 by which the longer waves were excited. The primary con- 



* Translated from the Sitzungsb. der Akad, der Wiss. Berlin, Dec. 13, 



1888. 



Phil. Mag. S. 5. Vol. 27. No. 167. April 1889. U 



