I 



THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



1/ 



[SIXTH SERIES.] 



OCTOBER 1902. 



L 



XL VII. On the Electrical Resonance of Metal Particles for 

 Light-Waves — Second Communication. By R. W. Wood, 

 Professor of Experimental Physics, Johns Hopkins Uni- 

 versity*. 



IN a previous paper f I have shown that granular deposits 

 of the alkali metals exhibit brilliant colours by trans- 

 mitted light. These colours were referred provisionally to 

 the electrical resonance of the minute particles for light-waves. 

 At the time of writing this paper, I was not acquainted with 

 Prof. ThrelfalPs interesting work on the optical properties 

 of metallic precipitates and his attempts to verify the polariza- 

 tion effects calculated by Prof. Thomson, to which I alluded. 

 I feel sure that the colours observed by Prof. Threlfall, and 

 those which I have observed, are to be referred to the same 

 causes. It was found that the immersion of the particles in 

 a liquid of high dielectric constant produced striking changes 

 in the colour of the transmitted light, the change corre- 

 sponding to a shift in the absorption-band towards the red 

 end of the spectrum. It has been recently shown by 

 Aschkinass and Shaefer % that the length of electromagnetic 

 waves to which a system of metallic resonators respond, is 

 increased by immersing the resonator system in a liquid of 

 high dielectric constant, which is obviously analogous to the 

 behaviour of the sodium and potassium films. It is also well 

 known that the position of the absorption-band of aniline dyes 



* Communicated by the Physical Society : read June 20, 1892. 

 t Proc. Physical Society, vol. xviii. ; Phil. Mag. April 1902. 

 \ Drude's Annalen der Phydk, vol. v. p. 489. 



Phil Map. S. 6. Vol. 4. No. 22. Oct. 1902. 2 F 



