748 PLUCKER ON THE DETERMINATION OF THE 



52. The experiments in the two preceding paragraphs possess 

 demonstrative power only when the position of equilibrium 

 with closed circuit is quite in the vicinity of the poles, so that 

 the tendency of the balance to return to the oblique position of 

 equilibrium before the closing of the circuit, acting in the same 

 direction as the diamagnetic repulsion, may not increase the ap- 

 pearance observed, and under certain circumstances alone pro- 

 duce it. It is therefore desirable to possess some modification 

 of the preceding experiments, in which no such disturbing action 

 occurs, which might so easily lead to false conclusions. 



I again suspended a watch-glass, jji which was placed a rounded 

 piece of bismuth, in the usual manner over the approximated 

 poles, to one arm of my great balance, and then by counterpoids 

 brought it into the horizontal position of equilibrium. At the 

 same time there was an arrangement which allowed of the watch- 

 glass being placed at different distances above the poles, by 

 raising or lowering the balance without the equilibrium being 

 disturbed. After this had been determined, the electro-magnetism 

 was produced successively from a different number of Grove's 

 cells. The magnetism and diamagnetism must then show their 

 presence by the attraction and repulsion of the watch-glass. The 

 magnitude of this attraction and repulsion, measured by the 

 raising and lowering of the watch-glass, is given in the following 

 series of experiments ; so that an approximate value may be 

 made of the preponderating magnetic or diamagnetic force: — 



I. The watch-glass in contact with the armature : — 



miUims, 



Number of cells 8 Repulsion 5*0 



2 ... 0*5 (scarcely) 



1 No perceptible effect 



II. The watch-glass raised 1'5 millim. : — 



