Lighty Heat y and Electricity. 217 



matter^ from which they can be separated and a portion trans- 

 ferred at pleasure from one surface to another without losing 

 their distinctive properties. I believe, therefore, that they must 

 be admitted to have a real existence, and cannot be regarded as 

 mere motion or as properties of matter. Assuming this, it ap- 

 pears to me that Wheatstone^s experiment with the revolving 

 mirror leaves no doubt that electricity consists of two self-repel- 

 lent fluids, and can no longer be considered merely the excess or 

 deficiency of a single fluid. 



In addition to the above properties, it is generally assumed 

 that there is a mutual attraction between the two fluids ; but a 

 careful consideration of the phenomena has led me to the conclu- 

 sion that this opinion is erroneous, and that they are mutually in- 

 different. 



An experiment of Mohr^s appears to me strongly in favour of 

 this view; viz. when an electrized body was placed at 1 centim. 

 from one end of an insulated cylinder (65 centims. long), the 

 neutral point was found to be at only 1 centim. from this extre- 

 mity of the cylinder. If attraction existed between the two 

 electricities, we should expect a large accumulation of the oppo- 

 site fluid at the end of the cylinder nearest to the charged body, 

 while the actual result appears plainly to indicate merely a re- 

 pulsion of the electricity of the same denomination with that of 

 the charged body. 



The facility with which the two fluids are separated even by 

 the slightest friction, and their not instantly disappearing again 

 (^as separate entities) when eliminated, first excited a suspicion 

 on this point, which has grown up into a firm belief that all the 

 statical phenomena supposed to establish mutual attraction can 

 be accounted for by the attraction of each for matter and the 

 self -repulsion of each fluid. Assuming, therefore, this to be the 

 constitution of the two electricities, and feeling bound to admit 

 no more causes than are necessary to account for phenomena, I 

 have arrived at the conclusion that 'Hhe two electricities,^^ in equal 

 quantities, each possessing self-repulsion (and mutually indif- 

 ferent to each other), possess those qualities which are, in my 

 mind, essential to a thorough explanation of the undulatory theory, 

 and constitute by their diffusion throughout space that ^^ ?ether^^ 

 whose existence is generally admitted as proved by the pheno- 

 mena of optics — the luminiferous vibrations of the two fluids 

 taking place in perpendicular planes, and always transverse to 

 the du-ection in which the light is propagated. 



On this hypothesis the cause of the intimate connexion be- 

 tween the state of the sun's photosphere and magnetic storms, 

 as well as other terrestrial electromagnetic phenomena, becomes 

 obvious ; and, as regards affections of molecules, I recognize in 



