64 W. 11. Grove, Esq., on (lie 



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 illustra- 

 tion, a string of fio-s. 



With magnetism we have many instances of the molecular change 

 which a ferreous or magnetic suhstance undergoes when magnetised. 

 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, shewed that the supernatant liquid in which magnetic 

 oxide had been formed, and which contains magnetic particles not 

 mechanically but chemically divided, exhibits when magnetised 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 magnetisation, then by repeated magnetisation in opposite di- 

 rections, 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 shewn to do), so a bar of soft iron 

 might be expected when subjected to rapid changes in its magnetic 

 state, to exhibit thermic effects, 



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

 mutator for changing the direction of the electricity, a bar of soft 

 iron was alternately magnetised in opposite directions ; and in a few 

 minutes a thermometer placed in an aperture in the iron shewed 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 in nowise be attributed to 

 conduction. 



The effect of electricity in the disruptive discharge as in the voltaic 

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

 difficulties of explanation on the dynamic theory. The brilliant 

 phenomenal effects of the electric discharge, and the apparent ab- 

 sence of change 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 

 effects 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 shewn 

 that the matter of the terminals or of the intervening medium is 

 changed, the necessity for the assumption of a fluid or ether ceases, 

 and, to say the least, a possibility of viewing electricity as a motion 

 or affection of ordinary matter is opened. 



To make evident to the audience the relation of the electrical dis- 

 charge to combustion and the fact that the terminals were themselves 



