and on the Theory of Magnetism. 89" 



pel as do those of a magnet; and in almost every point do they 

 agree. The following experiments will illustrate and confirm 

 the truth of these remarks on the action of the ring, helix, or 

 cylinder; and Will shew in what their actions agree with, and 

 differ (for there are differences) from, the action of a magnet. 



A small magnet being nearly floated in water by cork, a ping 

 of silked copper wire, fig. 16, having its ends connected with 

 the battery, was brought near its poles in different positions ; 

 sometimes the pole was repelled from, sometimes attracted into, 

 the ring, according to the position of the pole, and the con- 

 nexions with the battery. If the wire happened to be opposite to 

 the pole, the pole passed sideways, and outwards when it was re- 

 pelled, and sideways and inwards when it was attracted ; and on 

 entering within the ring and passing through, it moved sideways 

 in the opposite direction, endeavouring to go round the wire. 

 The actions also presented by INI. de la Rive's ring are actions 

 of this kind, and indeed are those which best illustrate the re- 

 lations between the ring and the pole ; some of them have been 

 mentioned, and if referred to, will be found to accord with the 

 statement given. 



With a flat spiral the magnetic power was very much 

 increased; and when the rings were not continued to the 

 centre, the power of the inner edge over the outer was well 

 shewn either by the pole of a needle, or iron filings. With the 

 latter, the appearance was extremely beautiful and instructive ; 

 when laid flat upon a heap of them, they arranged themselves 

 in lines, passing through the ring parallel to its axis, and then 

 folding up on either side as radii round to the edge, where they 

 met ; so that they represented, exactly, the lines which a pole 

 would have described round the sides of the rings : and those 

 filings which were in the axis of the rings, stood up in perpendi- 

 cular filaments, half an inch long and so as to form an actual axis 

 to the ring, tending neither one way nor the other, but according 

 in their form and arrangement with what has been described ; 

 whilst the intermediate portion also formed long threads, bend- 

 ing this way and that from the centre, more or less, according i& 

 they were further from, or nearer to, it. 



