386 Anniversary Meeting. [Nov. 30, 



of propagation, that is to say, precisely the vibrations in the undula- 

 tory theory of light according to Fresnel. But we have as yet 

 absolutely no guidance towards any understanding or imagining of 

 the relation between this simple and definite alternating motion, or 

 any other motion or displacement of the ether, and the earliest known 

 phenomena of electricity and magnetism the electrification of matter, 

 and the attractions and repulsions of electrified bodies ; the per- 

 manent magnetism of lodestone and steel, and the attractions and 

 repulsions due to it : and certainly we are quite as far from the 

 clue to explaining, by ether or otherwise, the enormously greater 

 forces of attraction and repulsion now so well known after the modern 

 discovery of electromagnetism. 



Fifty years ago it became strongly impressed on my mind that the 

 difference of quality between vitreous and resinous electricity, con- 

 ventionally called positive and negative, essentially ignored as it is 

 in the mathematical theories of electricity and magnetism with 

 which I was then much occupied (and in the whole science of mag- 

 netic waves as we have it now), must be studied if we are to learn 

 anything of the nature of electricity and its place among the pro- 

 perties of matter. This distinction, essential and fundamental as it 

 is in frictional electricity, electro-chemistry, thermo-electricity, pyro- 

 electricity of crystals, and piezo-electricity of crystals, had been long 

 observed in the old known beautiful appearances of electric glow and 

 brushes and sparks from points and corners on the conductors of 

 ordinary electric machines and in exhausted receivers of air-pumps 

 with electricity passed through them. It was also known, probably as 

 many as fifty years ago, in the vast difference of behaviour of the 

 positive and negative electrodes of the electric arc lamp. Faraday 

 gave great attention to it* in experiments and observations regarding 

 electric sparks, glows, and brushes, and particularly in his " dark 

 discharge " and " dark space " in the neighbourhood of the negative 

 electrode in partial vacuum. In [1523] of his 12th series, he says, 

 " The results connected with the different conditions of positive and 

 negative discharge will have a far greater influence on the philosophy 

 of electrical science than we at present imagine." His " dark dis- 

 charge " ([1544 1554]) through space around or in front of the 

 negative electrode was a first instalment of modern knowledge in 

 that splendid field of experimental research which, fifteen years later, 

 and up to the present time, has been so fruitfully cultivated by many 

 of the ablest scientific experimenters of all countries. 



The Royal Society's Transactions and Proceedings of the last forty 

 years contain, in the communications of Gassiot,f Pliicker, J Andrews 



* ' Experimental Eesearches,' Series 12 and 13, Jan. and Feb., 1838. 

 f ' Koy. Soc. Proc.,' vol. 10, 1860, pp. 36, 269, 274, 432. 

 ' Koy. Soe. Proc.,' vol. 10, 1860, p. 256. 



