ELECTRO-CHEMICAL POLARITY OF GASES. 371 



In the experiments I have detailed, the flame or visible 

 effect of the electric discharge coincided with the chemical 

 effect ; when the plate was positive, a small globule of flame 

 of a purple colour was visible on the part of the plate 

 attacked, and a bluish flame extended over an inch or more 

 of the needle. When the plate was -negative, a wider and less 

 defined disc of blue flame extended over the part of the plate 

 opposed to the positive point, like a splash of liquid thrown 

 upon it, and a pencil of light appeared on the point. Some- 

 times, but not always, this flame avoided the oxidated por- 

 tion, probably from its inferior conducting power ; and when 

 this was the case reduction took place in a much slighter 

 degree, or not at all ; sometimes, and I observed this particu- 

 larly with bismuth, the flame attached itself to the oxidated 

 portion, and then reduction immediately followed. Here, as 

 in all the electrical phenomena that I can call to mind, we 

 get the visible effects of electricity associated with physical 

 changes in the matter acting, changes of state in the terminals, 

 polarisation of the intervening medium, or both.* These ex- 

 periments furnish additional arguments for the view which I 

 have long advocated, which regards electricity as force or 

 motion, and not as matter or a specific fluid.f 



The chemical polarity of gases shown, as I believe, in this 

 paper, associates itself with an experiment which I made 

 known in a lecture at the London Institution in the year 

 1843,^ an d which was subsequently verified by Mr. Gassiot 

 with more perfect apparatus than I possessed, viz. that when 

 discs of zinc and copper are closely approximated, but not 

 brought in contact, and then suddenly separated, effects of 

 electrical tension are exhibited, the one disc making the elec- 

 troscope diverge with positive, and the other with negative 

 electricity, showing that the effects ascribed by Volta. to 



* Gases at present believed to be elementary probably undergo a quasi 

 chemical polarisation by electricity ; thus portions of oxygen are changed to 

 ozone, &c. See a recent paper by MM. Fremy and E. Becquerel, Comptes 

 Rendus, Paris, March 15. Note added to the proof, W. R. G., 1852. 



f Printed Lecture at the London Institution, 1842, p. 28. Correlation of 

 Physical Forces, p. 48. 



\ Lit. Gaz,, 1843, p. 39. 



Phil. Mag., October 1844. 



B B 2 



