252 Dr. Faraday on the Magnetic Affection of Light. 



able in every respect to judge any question arising on such a 

 subject as magnetism, made me anxious on two accounts ; for 

 first, I thought it possible I might really be in error respect- 

 ing the broad and general principle of magnetic action, which 

 I supposed I had discovered ; and next, that if right on that 

 point, I must have been sadly deficient in describing my re- 

 sults not to have conveyed a better impression to the minds of 

 those so competent to receive and understand. I therefore, 

 for my own sake, entered into an examination of this point ; 

 for though I am nearly indifferent to the fate of any specula- 

 tive or hypothetical view I may venture to send forth, I am 

 far from being so as regards the correctness of any announce- 

 ment I may make of a law of action or a new fact ; and having 

 carefully experimented on one or two of the cases of transverse 

 position assumed by certain bodies magnetic, as iron, I now 

 give the general result. 



Some good uniform peroxide of iron (being one of the sub* 

 stances which M. Becquerel experimented with) was prepared 

 and introduced regularly into a thin glass tube, 0*25 of an 

 inch in diameter and 1*4 inch long; it was then suspended by 

 a long filament of cocoon silk, and could be brought into any 

 position relative to one of the poles of a strong electro-mag- 

 net, which could be made to assume various forms by the use 

 of terminal pieces of iron. As peroxide of iron can occasion- 

 ally receive and retain a feeble magnetic state, it is necessary 

 the experimenter should be aware of the possibility, and guard 

 against its effect in producing irregular results. 



The pole of the magnet was in the first place a cone, of 

 which the base was 1*5 inch in diameter, its axis being in a 

 horizontal line. The cylinder of peroxide of iron was ad- 

 vanced towards the cone with its centre of suspension in a line 

 with the axis. When within the influence of the magnet, and 

 transverse to the axial line, it retained that position: but this 

 was a position of unstable equilibrium; for if the cylinder be- 

 came oblique to the axial line on either side, then the end 

 nearest to the cone approached towards it, being attracted, 

 and at last went up to and remained against it. But whether 

 directly across the axial line, and so in the position of unstable 

 equilibrium, or in any other position, the centre of gravity of 

 the whole was always attracted', an effect easily appreciated 

 with an electro- magnet by interrupting and renewing the ex- 

 citing current. 



As a contrast with diamagnetic bodies, I will state, that if 

 a similar cylinder of phosphorus, bismuth, or heavy glass be 

 placed in precisely the same circumstances, then the transverse 

 position is a position of stable equilibrium : if the cylinder be 



