the Laws of Magnetic Forces. 313 



that the polarity b may be considered as always without the limit 

 of its influence. If we add, at the same time, the neutralizing 

 effect of x upon b, then the action of b upon d may vanish alto- 

 gether. With respect to the distant polarity of m, that may, 

 when m is a very long bar, be always considered without the li- 

 mit of the action. In this case, therefore, the decrements of the 

 inductive force in be, as already stated, would seem to be altoge- 

 ther independent of any disturbance arising from the action of the 

 similar poles, although, in examining the reciprocal force exerted 

 between a mass of iron and a magnet, or between two magnets, 

 both these causes of disturbance may probably be in operation 

 within certain limits ; and they sufficiently explain the anomalous 

 results arrived at by different philosophers in their attempts to in- 

 vestigate the law of the absolute force exerted between two mag- 

 nets, or between a magnet and a mass of iron, when placed at diffe- 

 rent distances from each other : some asserting that it decreased 

 in the inverse ratio of the squares, and others in that of the 

 simple distance ; whilst many concluded, that it followed no re- 

 gular law whatever, but was different for different magnets. 



49. The results of the experiments with the repelling poles, 

 are equally interesting with those of the attracting, as furnishing 

 useful illustrations of the causes which operate in deranging the 

 uniformity of the result. The deviations, as may be anticipated 

 from what has already been shewn (43.), are more considerable 

 than in the former case. It will be perceived, that a few of the 

 first approximations in each case differ very little from the law 

 of the inverse square of the distance ; but they soon become very 

 irregular, and afterwards approximate to the inverse ratio of the 

 distance, until, in some instances, the pole of the weaker magnet 

 is apparently changed by the inductive influence, and the repul- 

 sive force is superseded by attraction. The most prominent 

 feature, therefore, in these experiments with the repelling poles, 



