254 Dr. Faraday on the Magnetic Affection of Light. 



a manner and to a degree easily comprehen- F . 



sible by those who consider the concentra- »• s « 



tion of magnetic force at the edges of the face. 



The same was the case with the former face 



of 25 inches. Either end of the cylinder of 



peroxide might be the end nearest to the face 



of the pole ; but the centre of gravity of the 



cylinder was in every case attracted by the 



magnet. 



Other cylinders of peroxide of iron of 

 different diameters and lengths were em- 

 ployed ; and when they were smaller in 

 length than the opposed faces of the magnetic 

 poles, the results were precisely the same. 

 _ A cylinder of paper, magnetic through the 

 presence of iron, was used and produced the 

 same results. 



Having been led to think that the disaggregation of the 

 peroxide of iron had considerable influence over these phe- 

 nomena, by obstructing and preventing the communication of 

 magnetic induction from particle to particle, and was far 

 more influential than the mere weakness of magnetic force, I 

 took some substances, even more weak in magnetic power 

 than the peroxide, and formed them into cylinders. The 

 substances were solution of proto-sulphate of iron, muriate of 

 cobalt and muriate of nickel, which were introduced into thin 

 glass tubes 0'25 of an inch in diameter and 1*4 inch long. 

 These, when suspended before the poles with their centres 

 of suspension in the axial line, did not act as the peroxide of 

 iron or the paper. They could indeed be kept in a position 

 parallel to the face of the pole, but this was a position of un- 

 stable equilibrium; and when the least removed out of that 

 position, the end nearest the magnet continued to approach 

 until it came in contact, and then the whole remained un- 

 changed. The action was precisely like that of a piece of 

 iron, but very inferior in energy. 



A saturated solution of proto-sulphate of iron was diluted 

 with five times its volume of water, and still showed precisely 

 the same phaenomena as the stronger solution: yet its magnetic 

 power was very far inferior to the magnetic force of the per- 

 oxide of iron, as was fully manifested by the extent of the at- 

 traction of the centre of gravity of the two portions of the sub- 

 stances. When the peroxide was under experiment, the sus- 

 pension-thread was drawn twice or even three times further 

 from the perpendicular than when the solution was used. 

 If a piece of iron wire be substituted for the cylinder of 



