266 Rev. Mr Scoresby on some of the Laws 



Hence it appears that the direct induction is vastly greater 

 than the influence communicated to the remote end of the bar, 

 being nearly five-sixths greater at the fourth length, about twice 

 as great at the third length, about thrice as great at the second 

 length, and about quadruple at the fourth length. 



The relative force of the inductive influence under the first 

 arrangement, — that is, as developed at the farthest end of the 

 bar, has been shown to be in the ratio of 1, ^th, Jth, i\th, 

 nearly, at the respective distances of 1, 2, 3 and 4 focal lengths 

 of the bar and magnet. But, under the latter arrangement, in 

 which the magnetism is directly induced on the same end of the 

 bar as that whose attractive energy is measured, a different ratio 

 is obtained. Taking the first tangent-difference of the first 

 series at 100, the relative energy of induction at the other dis- 

 tances successively become as 29.0, 8.6 and 4.5, which, expressed 

 fractionally, exhibit this series, in which the first is unity, {, ^|, 

 A J jg nearly. But, calling the first tangent of the second series 

 (110104) 100, the ratio becomes 100, 20, 5.3, or, fractionally, 

 as \, h io nearly. 



These results, exhibiting such considerable differences, may 

 be considered perhaps rather as perplexing than satisfactory. 

 They might seem to intimate, that, where the law of attraction 

 is so simple, the experiments not according with this law must 

 be erroneous. But simple as the law as to a single, separate 

 attraction is, the estimation of the variety of influences which 

 come into account, in these investigations, is far from being so 

 easy as at first sight it may appear. For, whilst the power of 

 the nearest pole tends to develope in the nearer end of the iron- 

 bar a magnetism contrary to its own, the tendency of the re- 

 motest pole of the magnet, being of a contrary polarity, is, in 

 the inverse proportion of the square of its distance, to alter the 

 magnetism developed by the other pole. But this is not all. 

 For each of the poles of the magnet have, at the same time, 

 their direct influence, however diminished in energy by increase 

 of distance, upon the remote end of the bar, which influence is 



east and west line of the compass. Still, however, the smallest error of ob- 

 servation or position, where the angle is so great, necessarily produces very 

 considerable differences in the tangents, so as to render the observation of 

 the nearest position unsatisfactory. 



