256 M. F. Reich on Diamagnetic Action. 



ratio does not differ mucli from that of the squares of the cur- 

 rents. In general, however, the latter ratio is not quite attained, 

 which is explained by the fact that the distance increases with 

 the repulsion. We are therefore certainly justified in assuming 

 that the diamagnetic repulsion is proportionate to the square of 

 the magnetic intensity which produces the repulsion, and is 

 therefore a product of a polarity excited by influence in the dia- 

 magnetic body. 



With reference to the concluding paragraph of M. Reich's in- 

 teresting paper, I may be permitted to express the opinion that 

 the result which he has corroborated is not, in itself, a proof that 

 the diamagnetic force is a polar force. It undoubtedly proves 

 that the repulsion is due to a state of excitement into which the 

 bismuth is thrown by the influencing magnet ; but it does not, 

 I think, prove the dual or j^olar nature of that excitement. True, 

 we have no example in nature of a similar excitement that is not 

 polar; but such is at least conceivable, although as yet unob- 

 served. For this reason I thought it necessary, in the paper to 

 which M. Reich has referred, to show that the excitement of 

 diamagnetic bodies is of a duplex character ; and that the attrac- 

 tions and repulsions of a bar of iron under magnetic influence, 

 have their exact antitheses in the repulsions and attractions of a 

 bar of bismuth acted upon by the same forces. 



In repeating experiments such as those described in the paper 

 to which M. Reich has alluded, a certain acquaintance with the 

 delicate mechanical conditions required to be fulfilled is necessary 

 to success. Knowing this, it was not a matter of surprise to me 

 to learn that M. Matteucci failed, for a time, to realize my results, 

 and was consequently led to doubt their existence. Hence, I 

 suppose, his desire to see my experiments repeated with M. 

 Reich's apparatus. The doubts referred to, I am happy to say, 

 no longer exist, as through the kindness of M. Matteucci him- 

 self I learn that he has recently arrived at a complete corrobora- 

 tion of my experiments. 



I may further remark, that in a paper now in the course of 

 printing for the Philosophical Transactions, the conditions laid 

 down by M. Matteucci for the " rigorous demonstration of dia- 

 magnetic polarity " are strictly fulfilled ; so that, as far as I am 

 aware, no single objection that has ever been made against the 

 fact of diamagnetic polarity remains at the present time un- 

 answered. Finally, with reference to the bearing of this question 

 upon that of magnecrystallic action, I would refer the reader to 

 a paper in the last Number of this Journal. 



J. T. 



