Intelligence and Miscellaneous Articles. 75 



passage from one to the other of the two extreme forms of the 

 phenomenon does really take place. — liendieonti della Recde Acca- 

 demia dei Lincei, vol. iv. pp. 151, 189; Journal de Physique, 

 Nov. 1890. 



ON THE PHOTOGRAPHIC ACTION OF ELECTROMAGNETIC WAVES. 

 BY FRANZ VON DOBRZYNSKI. 



For several months I have been engaged in investigating the 

 photographic action of electromagnetic waves. On May 1 I 

 observed an indication of this action, and on July 9 the action 

 itself. 



The electromagnetic waves were obtained by the method of 

 Hertz. They acted on dry bromide of silver and gelatine ' Nys ' 

 plates procured from Greissler in Bonn. 



The plane of the plates either included the axis of the vibrator or 

 was at right angles to it. The exposure was three hours. No 

 sensitization of the plates was made. The development and 

 fixation took- place in the ordinary manner by ferric oxalate and 

 hyposulphite. 



The action was visible after development and fixation by the 

 appearance of alternating bright and dark bands across the direction 

 of vibration of the waves, or by the appearance of dark bands in 

 the direction of the vibration. Both kinds of bands could occa- 

 sionally be observed together. 



In many experiments the plates were covered with tinfoil. 

 Portions of the coating of the tinfoil were cut away. The tinfoil 

 did not prevent the formation of bands. This points to the fact 

 that the chemical action which here comes into play is not a 

 primary one. 



The cross bands suggested stationary vibrations. They might 

 be due to reflexion from the sides of the wooden box, by which the 

 plates were protected from the influence of extraneous rays ; but 

 they might also owe their origin to reflexion from the side of the 

 room*. 



The only experiment which could be made with a reflecting 

 metal ball was not in disagreement with this view; the cross 

 bands were now more distinct and regular. 



If this view is correct, it may be concluded that waves of from 

 0-6 to 20 centim. are effective. 



The complete description of the mode of experimenting I will 

 defer until 1 communicate further investigations in this direction. 

 — Wiener Berichte, October 9, 1890. 



* The plates often contained two systems of cross hands. These 

 would represent different waves which the vibrator emits in the sense of 

 the discovery of Sarasin and De la Rive, and in that of the view stated 

 above. 



