440 . Mr. Fox on the Laws of Magnetic Attraction. 



The magnets I employed exerted only one half 'their force 

 when from contact they were separated about the two thou- 

 sandth of an inch from each other ; one quarter their force when 

 the distance between them was one thousandth of an inch; 

 one eighth when it amounted to \hzfve hundredth part of an 

 inch ; and so on, in the direct inverse ratio of the distance, 

 until they were one eighth of an inch or more asunder; and as 

 they were still further removed from each other, the law of 

 attraction gradually approximated to the inverse ratio of the 

 square of the distance. 



It is well known that a magnet has a portion of its lateral 

 force suspended when its poles are made to approach the dis- 

 similar poles of two other magnets, and that it is reduced 

 to a state of comparative neutrality when those poles are 

 brought into actual contact ; and this is doubtless the case 

 with the numerous minute magnets of which loadstone dust 

 consists when their tendency to diverge is overcome, or rather 

 superseded, by strong opposite attractions, and they become 

 arranged in parallel straight lines. This arrangement takes 

 place at greater distances with strong magnets than with weak 

 ones, and in like manner the law changes at greater distances 

 in the former case than in the latter. The loadstone dust 

 seems to explain the arrangement of the invisible magnetic 

 elements, supposing them also to possess polarity ; and that 

 they do, may be inferred, not only from analogy, but still 

 more strongly from the law which I have shown to prevail 

 between magnets at very small distances from each other ; 

 for this phagnomenon cannot, I think, be reconciled with the 

 idea of forces emanating in all directions from a centre or 

 centres, whilst it seems to be in strict accordance with the 

 assumed accumulation of energy at the opposite poles of the 

 magnetic elements. 



Having more than a year ago announced the existence of 

 the law in question as a general one throughout a considerable 

 series of minute distances, and also endeavoured to show the 

 cause of it, I have felt some hesitation in again recurring to the 

 subject, but I have ventured to do so, conceiving that it will 

 be found to merit more attention than it has hitherto obtained: 

 and when I consider the phsenomena of crystallization and 

 those of the polarization of light, &c, I am inclined to believe 

 that even molecular attraction or affinity may, within certain 

 distances, be governed by similar laws; and this opinion, 

 which I have long entertained, has been strengthened by the 

 beautiful experiments in illustration of the laws of electrical 

 attraction which my friend W. S. Harris exhibited in Dublin 

 before the Physical Section of the British Association. 



