supposed Polarity of Diamagnetic Bodies, 105 



If a bar of iron of the same size be fixed in the equatorial 

 position a little below the plane in which the diamagnetic bar 

 is moving, the latter will proceed to the equatorial position 

 with much greater force than before, and this is considered 

 as due to the circumstance, that, on the side where the iron 

 has N polarity, the diamagnetic body has S polarity, and that 

 on the other side the S polarity of the iron and the N polarity 

 of the bismuth also coincide. 



2692. It is however very evident that the lines of magnetic 

 force have been altered sufficiently in their intensity of direc- 

 tion, by the presence of the iron, to account fully for the in- 

 creased effect. For, consider the bar as just leaving the axial 

 position and going to the equatorial position ; at the moment 

 of starting its extremities are in places of stronger magnetic 

 force than before, for it cannot be doubted for a moment that 

 the iron bar determines more force from pole to pole of the 

 electro-magnet than if it were away. On the other hand, 

 when it has attained the equatorial position, the extremities 

 are under a much weaker magnetic force than they were sub- 

 ject to in the same places before; for the iron bar determines 

 downwards upon itself much of that force, which, when it is 

 not there, exists in the plane occupied by the bismuth. Hence, 

 in passing through 90°, the diamagnetic is urged by a much 

 greater difference of intensity of force when the iron is present 

 than when it is away ; and hence, probably, the whole addi- 

 tional result. The effect is like many others which I have 

 referred to in magnecrystallic action (24<87-2497.)5 and does 

 not, I think, add anything to the experimental proof of dia- 

 magnetic polarity. 



2693. Finally, I am obliged to say that I can find no ex- 

 perimental evidence to support the hypothetical view of dia- 

 magnetic polarity (2640.), either in my own experiments, or 

 in the repetition of those of Weber, Reich, or others. I do 

 not say that such a polarity does not exist ; and I should think 

 it possible that Weber 5 by far more delicate apparatus than 

 mine, had obtained a trace of it, were it not that then also he 

 would have certainly met with the far more powerful effects 

 produced by copper, gold, silver, and the better conducting 

 diamagnetics. If bismuth should be found to give an)- effect, 

 it must be checked and distinguished by reference to the posi- 

 tion of the commutator, division of the mass by pulverization, 

 influence of time, &c. It appears to me also, that, as the 

 magnetic polarity conferred by iron or nickel in very small 

 quantity, and in unfavourable states, is far more readily indi- 

 cated by its effect on an astatic needle, or by pointing between 

 the poles of a strong horseshoe magnet, than by any such 



