MAGNETISM. 



net, or line joining its two poles, as in 

 the situations represented in Jig. 8. The 



'Fig. 8. 



ends, s, s, of the bars B, C, adjoin- 

 ing the north pole N of the magnet A, 

 will still become south poles by induc- 

 tion, and the ends ra, ra, north poles. 

 Under these circumstances, if the incli- 

 nation be less than a right angle, as in 

 the case of C, the opposite pole of the 

 magnet s begins to exert an inductive 

 influence on the other end of the bar n, 

 which concurs with that of the pole N 

 in rendering n a north and s a south 

 pole. The most favourable position for 

 the bars receiving the full inductive in- 

 fluence of both poles is that of parallelism 

 with the magnet A, as shown mjig. 9. 

 Fig. 9. 



(30.) Complicated effects result from 

 bringing the magnet in contact with 

 other parts than the ends of a piece of 

 iron. Thus, if the north Fig. 10. 

 pole of a magnet be placed ||||[||S 



in the middle of an iron 

 bar, as in Jig. 10, both 

 extremities of the bar are 

 rendered north poles, while 

 the middle is a south 

 pole. 



(31.) If the north pole of a magnet be 



placed on the centre of a round iron 



plate (Jig. 11), so that its axis may be 



Fig. 11. Fig. 



perpendicular to it, the plate will have a 

 south pole in its centre, and every part 

 of its circumference will have the pro- 

 perties of a weak north pole. If the plate 

 have the form of a star (Jig. 12), each 



of the points will have a stronger 

 northern polarity than in the last case. 

 Analogous effects may be observed in 

 pieces of iron of an irregular shape 

 when acted upon by a magnet ; the part 

 immediately adjoining to the north pole 

 of the magnet acquires the properties of 

 a south pole, and all the remote protu- 

 berances have a feeble northern polarity. 



$ 5. Complex Induction. 



(32.) When two magnets are placed 

 so as to exert an inductive influence on 

 the same bar, it will depend on their re- 

 lative position, whether they shall con- 

 spire to produce the same polarities in 

 the ends of the bar, or whether they 

 shall oppose each other, and produce 

 contrary polarities. If the bar B, fig. 

 13, lie between the two magnets A and 



Fig. 13. 

 A T* c 



S tf " '" S 



C, and be in the same line with them, 

 and if N, the north pole of A, be adja- 

 cent to S, the south pole of C, the inter- 

 mediate bar B will receive a magnetism 

 of the same kind from the inductive 

 power of both the magnets, its south 

 pole s being adjacent to N, and its 

 north pole n to S. Its magnetic power 

 will, therefore, be considerably greater 

 from the united influence of the two 

 magnets, than it would have been from 

 the influence of one only. 



(33.) It may here be observed that the 

 order in which the poles of these pieces 

 A, B, and C, succeed one another, is 

 exactly the same as that which obtains 

 in the successive induction of magnetism 

 along a series of iron bars, as in fig. 5. 

 Now the same consequences follow from 

 this arrangement in the one case as in 

 the other. We have just seen that when 

 C is a bar already rendered magnetic, 

 the magnetism of the iron bar B, which 

 the magnet A had induced upon it, is 

 increased by the presence of C. In like 

 manner, we find that the magnetism of 

 the bar B, in the case above referred to, 

 fig. 5, is increased by the presence of ano- 

 ther piece of iron C, placed at its end, al- 

 though that piece, previously to its being 

 so placed, was entirely free from magnet- 

 ism. This increase is owing to the 

 piece C having become magnetic by its 

 position with respect to B, which had 

 itself been rendered magnetic by the 

 vicinity of the magnet A. C having 

 thus become a temporary magnet by 



