SI 6 Mr HARRIS'S Experimental Inquiries concerning 



The cylinder of soft iron ac, Fig. 17, being suspended as in 

 the former experiments, and the bars placed immediately under 

 it in succession, the intensity of different points between the 

 centre and poles were carefully ascertained, by moving along the 

 magnet under examination, so as to bring these points succes- 

 sively under the suspended iron ; and the constant distance as- 

 certained and preserved by means of the moveable scale and the 

 adjusting screws, as in the former experiment (23). 



In this experiment, it is essential to reduce the action to the 

 point immediately under the suspended iron, a condition which, 

 in a purely theoretical sense, is not possible to be fulfilled ; in- 

 asmuch as the attractive force will be involved in the combined 

 action of all the other points of the bar. We may, however, un- 

 der the circumstances already considered (22), approximate so 

 nearly to it, that the resultant will not differ very materially 

 from that of the force at a ; so that, for a long series of points, 

 we may obtain a uniform law, as appears evident by the fol- 

 lowing Table, in which D signifies the distance from the centre 

 in hah inches, and F the corresponding forces of attraction ; the 

 constant distance of the suspended iron ae being placed imme- 

 diately after the letters AB, which denote the respective bars. 



TABLE XVI. 



From these results, it would appear, that the law of the dis- 

 tribution varies directly as the square of the distance from the 



