Royal Institution. 313 



In the cases of heating, or ignition of a conjunctive wire or con- 

 ducting body through which what is called electricity is transmitted, 

 we have many evidences that the matter itself is affected, and in some 

 cases temporarily, in others permanently changed ; thus if a wire of 

 lead is ignited to fusion by the voltaic battery, the fused lead being 

 kept in a channel to prevent its dispersion, it gradually shortens, 

 and the molecules seem impressed with a force acting transversely 

 to the line of direction of the electricity ; at length the lead gathers 

 up in nodules which press on each other as do, to use a familiar 

 illustration, a string of figs. 



With magnetism we have many instances of the molecular change 

 which a ferreous or magnetic substance undergoes when magnetized. 

 If the particles are free to move, as for instance iron filings, they 

 arrange themselves symmetrically. An objection may be made 

 arising from the peculiar form of the iron filings, but Mr. Grove, in 

 the year 1845, showed that the supernatant liquid, in which magnetic 

 oxide had been formed, and which contains magnetic particles not 

 mechanically but chemically divided, exhibits when magnetized a 

 change in the arrangement of the molecules, as may be seen by its 

 effect on transmitted light ; — a molecular change is also evidenced 

 by the note or sound produced by magnetism, and by other effects. 



Assuming that the molecules of iron change their position inter 

 se upon magnetization, then by repeated magnetization in opposite 

 directions, something analogous to friction might be produced ; and 

 just as a piece of caoutchouc when elongated produces heat (as it 

 was on this occasion experimentally shown to do), so a bar of soft 

 iron might be expected, when subjected to rapid changes in its mag- 

 netic state, to exhibit thermic effects. 



With the aid of the large magnet of the Institution and of a 

 commutator for changing the direction of the electricity, a bar of 

 soft iron was alternately magnetized in opposite directions ; and in a 

 few minutes a thermometer placed in an aperture in the iron showed 

 a rise of temperature of 1°'5 Fahrenheit: the bar being separated 

 from the magnet by flannel, and the magnet being at a notably lower 

 temperature than the bar, this heat could nowise be attributed to 

 conduction. 



The effect of electricity in the disruptive discharge, as in the vol- 

 taic arc and the electric spark, would seem at first sight to offer 

 greater difficulties of explanation on the dynamic theory. The bril- 

 liant phsenomenal effects of the electric discharge, and the apparent 

 absence of ehange in the matter affected by it, would at first lead 

 the observer to believe that electricity was a specific entity. 



With ordinary flame or the apparent effects of combustion, how- 

 ever, the idea has to a great extent been abandoned that such visual 

 effect! are due to specific matter, and it is regarded by many as an 

 intense motion of the particles of the burning body. So with elec- 

 tricity, if in regard to the disruptive discharge it can be shown that 

 the matter of the terminals or of the intervening medium is changed, 

 the necessity for the assumption of a fluid or rcther ceases, and, to 

 ?ay the least, a possibility of viewing electricity as a motion or affec- 

 tion of ordinary mutter is opened. 



