4 R. W. Fox on Magnetic Attraction and Repulsion. 



at a smaller distance than when two magnets attract each 

 other; but when soft iron is made to repel a magnet, by being 

 in contact with the corresponding pole of another magnet, 

 the law approximates to that of the simple inverse ratio, even 

 at very considerable distances; indeed, in this case the law of 

 the inverse ratio of the squares scarcely ever obtained at di- 

 stances at which the magnetic action was very perceptible in 

 the method which I adopted to ascertain these forces ; and 

 when they were brought near each other, the repulsive force 

 rapidly diminished, and ultimately became attractive. This 

 also occurred, although in a less degree, when the similar poles 

 of two magnets acted upon each other, if they materially, or 

 even moderately differed in intensity. 



The attraction under these circumstances at the commence- 

 ment seemed to be in the duplicate inverse ratio, and on the 

 magnets being brought nearer together, in the simple inverse 

 ratio, of the distance. 



It may here be observed that the force of attraction was 

 considerably greater when the edges only of the magnets were 

 in contact, than when their whole surfaces were together, 

 which is perhaps attributable, in part at least, to the contact 

 being more complete in the former case than in the latter. 

 Hence it seems that the small magnets I employed lost one 

 half their force at the distance of about ^ ife o tn °^ an lnc ^t olle 

 quarter at y^^th, &c. 



It is well known that pulverized magnetic iron, or iron 

 filings, will diverge at each pole of a magnet; and I found that 

 on making two dissimilar poles approach each other, this di- 

 vergency was not changed till they were brought within 

 certain degrees of approximation, in fact, sufficiently near to 

 produce the change in the law above mentioned : the diver- 

 gency then diminished, till the fibres of powdered loadstone 

 became parallel to each other, and to the axis of the attract- 

 ing poles, and so they continued till the magnets were in ac- 

 tual contact (see figs. 1. and 2.). This experiment seems to 

 afford distinct evidence of the change which the magnetic 

 elements sustain, and sufficiently explains the immediate 

 cause of the alteration in the law of the attractive force which 

 has been noticed. 



When similar poles are gradually made to approach each 

 other, the divergency of the adhering particles of loadstone is 

 sooner disturbed than in the case of attraction, it being more 

 and more increased, till the ferruginous filaments are repelled 

 at nearly right angles to the axis of the magnet ; and if the 

 magnets differ much in force, the filaments attached to the 

 weaker one are so far driven back as to become nearly paral- 



