402 EXPERIMENTAL INVESTIGATIONS. 



diverge. Now raise the upper plate by a glass handle : the 

 leaves collapse in proportion as it is raised and again diverge 

 as it is depressed. It should be recollected that the plates 

 are electrified by the same electricity, and are always metalli- 

 cally connected by the fine wire, in which respect this differs 

 from ordinary induction experiments. It may be said that 

 here the mechanical force is given by the hand ; but this is 

 only in part : the repellent effect of electricity does part of the 

 work, and would be therefore expended ; it is analogically as 

 though a man were to add his force to the piston-rod of a 

 steam-engine, which would not prevent the loss of heat by the 

 dilating steam. I had hoped to have carried the experiments 

 farther and examined the relative quantities, but unfortunately 

 I have no time for such enquiry, and must leave it to others 

 who have more leisure. 



NEW METHODS OF PRODUCING AND FIXING 

 ELECTRICAL FIGURES. 



Phil. Mag., January 1857. 



A CLASS of figures produced on polished surfaces by elec- 

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

 on glass, mica, or polished metal, was made known by M. 

 Karsten,* who refers in his memoir to the previous results of 

 Moser and Riess, the latter having given the name of roric 

 figures to those 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 in 

 fixing these figures by exposing them to the vapours of iodine 

 or mercury, f and that when an insulating substance was inter- 

 posed between the object and the recipient plate the figures 

 were not formed. J 



This class of experiments possesses much interest, as 

 showing the molecular changes accompanying electrical phe- 



* Archives de VElectridte, vol. ii. p. 647 ; iii. p. 310 ; iv. p. 457. 

 f Ibid.) vol. ii. p. 651. 

 \ Ibid.) vol. iv, p. 464. 



