Dr. Faraday on the Magnetic Affection of Light. 253 



moved from it, it returns by vibrations into it; and during the 

 whole time the centre of gravity of the mass is repelled. 



A square end was now given to the pole of the magnet, the 

 face opposed to the cylinder of peroxide being 1*75 inch 

 wide and of an equal height. The axial line is that which 

 passed horizontally from the middle of this face, and took its 

 course through the centre of gravity of the cylinder, which was 

 also its centre of rotation. When the cylinder was at any di- 

 stance less than 0-3 of an inch from the face of the pole, it 

 stood parallel to the face, and therefore transverse to the axial 

 line : being moved out of this position, it resumed it, so that 

 the position was one of stable equilibrium. At distances a 

 little greater this became a position of unstable equilibrium, 

 and two positions of stable equilibrium were found equally in- 

 clined on the opposite sides of the transverse position, be- 

 coming more and more oblique to it as the distance was in- 

 creased. Both the transverse positions and the oblique po- 

 sitions were easily referable to the concentration of the lines 

 of magnetic force at the edges of the square end of the mag- 

 net. Effects due to the same cause have already been pointed 

 out in the Experimental Researches (2298, 2299, 2384)*. 



In every position of the cylinder of peroxide before this 

 magnetic pole, the peroxide, as a mass, was attracted. 



By using another termination of iron, the end of the pole 

 opposite the peroxide was enlarged in its horizontal dimen- 

 sions to 2*5 inches. All the former phenomena recurred ; 

 but the distance between the face of the pole and the tube of 

 peroxide could be increased to one inch or more, before the 

 tube began to assume the oblique positions. 



A third termination presented a face having 3*5 inches of 

 horizontal extension : the phaenomena were here precisely the 

 same, but the distance could be increased to 1*75 inch before 

 the cylinder ceased to be parallel to the face, and began to 

 acquire an oblique position. 



For the complete comprehension of this and other effects 

 due to the form of the face of the pole, and the concentration 

 of the lines of magnetic force passing through the air near the 

 edges, I will describe the positions assumed by the cylinder 

 of peroxide, when its centre of suspension was preserved at a 

 constant distance from the face of the pole, but was carried 

 into different positions on one side or the other of the axial 

 line. These are represented in the figure ; by which it will 

 be seen, that as the peroxide was carried to one side or the 

 other of the axial line it became inclined to that line, in 



* Philosophical Transactions, 1846, pp. 32, 48. 



