the Laws of Magnetic Forces. 



291 



under the suspended cylinder x ; for it is not difficult to shew, 

 that, in consequence of the other forces being small, and other- 

 wise caused to act at very small angles, the resultant cannot 

 differ materially from that of the force a x, and thus we approxi- 

 mate very nearly to a simple result. Moreover, it could be at 

 all times ascertained experimentally if any other point b, Fig. 9, 

 exerted an influence on the index, by withdrawing the iron and 

 magnet until a arrived at b, the induced force in the iron being 

 the greatest. In this instance, the index was not influenced 

 when the iron a b was withdrawn for a very short distance from 

 under the suspended cylinder oc ; so that the force of the attrac- 

 tion might, without any considerable error, be supposed to ema- 

 nate from the point a, the magnet M being preserved at all times 

 without the attracting limit. 



23. The magnet and iron described (21) being placed hori- 

 zontally, with a small moveable scale my, to indicate the con- 

 stant distance a x, as in Fig. 9 ; the same process was repeated 

 as before explained (19). The results are given in the next 

 Table, the distance ax being constantly made equal to two- 

 tenths of an inch. 



In this Table, D signifies the distance be, and F the corre- 

 sponding forces in degrees, 5 being equal to one grain. 



TABLE III. 



The trifling differences observable in some of the numbers are 



VOL. XI. PART II. 



o o 



