New Methods of producing and fixing Electrical Figures. 63 ' 



be made applicable for technical purposes. That the light from 

 the points, even when the interniptor moves most quickly, re- . 

 mains very plainly intermittent, may be easily proved by causmg 

 an illuminated object to move quickly to and fro J" general 

 the induction current will always develope less heat than the 

 voltaic current applied to produce it ; and although this property 

 does not stand in direct relation to the generation of light by the 

 coal-points, still we cannot think of producing the latter without 

 a strong development of heat. 



Vlir On some New Methods of producing and fixing Electrical 

 ' Figures. By W. R. Grove, Esq., V.P.R.S. ^x.* 



A CLASS of figures produced on polishedsurfacesby electrizing 

 a metallic bas-relief, such as a coin or medal placed on 

 glass, mica, or polished metal, was made known by M Karstenf, 

 who refers in his memoir to the previous results of Moser and 

 Riess, the latter having given the name of rone hgures to tliose 

 produced by electrical discharges on account of their becoming 

 visible, as Karsten's did, when breathed on. M. Karsten states 

 that he had but imperfectly succeeded m fixmg these figures by 

 exposing them to the vapours of iodme or niercury J, and tha 

 when an insulating substance was mterposed between the object 

 and the recipient plate, the figures were not formed§. 



This class of experiments possesses much interest as showing 

 the molecular changes accompanying electrical phaenomena; and 

 believing, as I have for many years, that electricity is no kng 

 else but motion or change in matter, a force and not a fluid 1 

 have recently made some experiments to ascci-tain whether simiiai 

 efflcts took place in cases where electrical light is visible upon 

 insulated surfaces only, a great number of experiments having 

 already shown that the particles of metals or conducting bodies 

 are nroiccted when the electrical spark proceeds from them. 



M Du Moncel has shown that when two plates ot glass coated 

 respectively on their exteriors with metallic plates are keptsepa- 

 rate and elLtnzed, a brilliant electrical light is seen between the 

 plates 11 I th.mght I might render evident the molecular change 

 wh eh behevedlo be taking place on the opposed surfaces of 

 glass in such cases, and the following exioenments selected from 

 n any others, will, 1 think, prove that this is the tact. 



TMo dates of wmdow glass, 3 by 3^ inches, wei^ immei^ed 

 in nitric acid, then washed, and dried by a clean silk-handker- 



* Communicated by the Author. - 



t Arckio.s ae I'ElectucU^, vol. n. p. M7 ; -jP,f Jj,- ^ ;.y4. 

 ■•■ Ibiil vol. 11. p. ''«>i. ,'. 



II Notices sur I'appftreil de Ruhmkorff, p. 4(). 



