THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCP:. 



[FOURTH SERIES.] 



APRIL 1856. 



XXXI. On Diamagnetic Action. By F. Reich*. 



IT is still a point of discussion whether the repulsion exercised 

 by a magnetic pole upon a diamagnetic body is the effect of 

 a polarity induced in the latter or not. Mr. Tyndall has recently 

 founded a decision of the question on the consideration, that the 

 diamagnetic repulsion must increase in the simple ratio of the 

 strength of the current if it be simply an action of the magnetic 

 pole upon the unchanged substance of the diamagnetic body ; on 

 the contrary, the inci-ease must be as the square of the strength 

 of the current if the action be due to an excited polarity; just as 

 the action of one magnet upon another, whose magnetism is 

 unchanged by the former, is simply as the current strength, 

 whereas upon a piece of soft iron it is as the square of the mag- 

 netic intensity. Partly by his own experiments, and partly by 

 others previously made by E. Becquerel, Mr. Tyndall has shown 

 that the diamagnetic repulsion augments with the square of the 

 current, which is a new proof of the polarity of a diamagnetic 

 body. 



I should not have thought of subjecting these experiments to 

 a corroborative repetition, were I not called upon by M. Mat- 

 teucci to do so, by means of the torsion balance which I had 

 constructed for the determination of the density of the earth ; 

 and as the experiments have now been made, I hope that their 

 publication will not be altogether without interest. 



On one end of the torsion balance hangs a sphere of bismuth 

 weighing 484-15 grms., surrounded by a cylindrical wooden 

 chamber coated within and without with tinfoil. On a level 



* From Poggendorff's Annalen, vol. xcvii. p. 283. 

 Phil. May. S. 4. Vol. 11. No. 72. April 1856. S 



