MAGNETISM. 

 Fig. 35. 



21 



in the direction of their polarities, which 

 is that of the tangent to the magnetic 

 curve : thus affording a beautiful ocular 

 exemplification of the mathematical pro- 

 perties of these curves. 



(86.) By continuing to tap upon the 

 paper, the filings arrange themselves still 

 more visibly into separate lines ; but 

 here a curious, and perhaps unlocked for 

 phenomenon presents itself. The lines 

 gradually move and recede from the 

 magnet, appearing as if they were re- 

 pelled, instead of attracted, as theory 

 would lead us to expect. This arises 

 from the circumstance that each particle 

 of iron, or cluster of particles, is thrown 

 up into the air by the shaking of the 

 paper, and, while unsupported, imme- 

 diately turns on its centre, and acquires 

 a position more or less oblique to the 

 plane of the paper. This is shown in 

 Jig. 36, in which M represents a section 



Fig. 36. 



of the magnet, P P a section of the 

 paper, and // the position of the fila- 

 ments of iron thrown up into the air. 

 The end of each filament nearest to the 

 magnet is thus turned a little down- 

 wards, and the filament falls upon the 

 paper at a point a little more distant 

 than that which it before occupied ; and 

 thus, step by step, it moves further and 

 further from the magnet, till it reaches 

 the edge of the paper and falls off. 



(87.) When the magnet, instead of 

 being beneath the paper, is held above 

 it, the effect is just the reverse. In 

 this latter case, the lower ends of the 

 filaments having a tendency to turn 

 towards the magnet, the filings gradually 

 collect under it, when made to dance by 

 the vibrations of the paper, instead of 

 falling outwards as they did before. 

 This will be rendered apparent by fig. 

 37, where the letters indicate the same 

 objects as in the preceding figure. 



Fig. 37. 



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