334. James Elliot on certain 



actly to the case of the top when its velocity is not sufficient 

 to prevent it from falling. But if the velocity is greater than 

 that which is necessary to keep the nearest point of the ring 

 at a uniform distance from P, then PB will be greater than 

 PA, and the ring will become less and less eccentric, the 

 circle, or rather the curve, ADEF gradually enlarging till it 

 coincide with the ring, and the curve CO gradually contract- 

 ing till it disappear in the central point. The ring then be- 

 comes perfectly concentric with the planet, and the state of 

 stable equilibrium is restored. The latter case corresponds 

 again to the case of the top whose velocity is sufficient to 

 cause it to rise towards a vertical position.* 



Such was my theory, formed independently of experiment, 

 but afterwards confirmed by it. After repeated trials, I suc- 

 ceeded, by means of the apparatus represented in the follow- 

 ing drawing, in showing it. 



M is a magnet supported on a stand, and R, an iron ring 

 capable of revolving rapidly. E is a wooden support to con- 

 tain the ring. D is an appendage employed for the purpose 

 of bringing the centre of gravity of the whole to the same 

 level with the point of support, and so getting rid of any 

 conical motion which the axis of the ring might have inde- 

 pendently of the magnet. The ring R, its support E, and 

 the appendage D, revolve together upon a hollow on the top 

 of the stem C, and are set in motion before the magnet is 

 introduced. It is then found that the ring, when revolving 

 with sufficient rapidity, is not, as Laplace asserts, in instable 

 equilibrium, but that the rotatory motion is able to preserve 

 it from collision with the magnet. We find also precisely 

 the same eccentric revolution which was anticipated by theo^ 

 ry, and corresponding exactly to that which, as I have pre- 

 viously stated, is observed in Saturn's ring itself. 



The power of preserving the equilibrium, in the model, is 

 so decided, that the whole apparatus may be turned consi- 

 derably on one side, without derangement, the ring accom- 



* If the top never reach a perfectly vertical position, neither will the ring 

 ever become perfectly concentric with the planet. But it is sufficient if we 

 establish that it will constantly tend towards that state, approaching indefi- 

 nitely near to it. 



