Chap. 6.] How to mcreafe tbe Power of Magnets. 49 



is produced by electricity. If a bar inlaid horizon- 

 tally to the magnetic meridian, and fubjected to the 

 electric fhock, whatever may be the direction in which 

 the {hock enters, that extremity which is pointed to- 

 wards the north, will be the north pole j and if the 

 bar (lands perpendicular, it will follow the ufual law 

 of communicated magnetifm, that is, in this hemi- 

 fphere, the end which is next to the earth will be the 

 north pole *. Lightning is the mod powerful of all 

 natural agents in producing immediate magnetifm ; 

 it will, in an inftaht, render* hardened free! ftrongly 

 magnetic, and will invert the poles of the magnetic 

 needle f. 



One of the moft fingular properties of the magnet 

 is, the increafe of power which may be added to it by 

 gradually increafing the weight it fuftains ; and on the 

 other hand, it wi)l gradually, by difufe, lofe much of 

 its natural ftrength . If a magnet is hung up with a 

 weight of iron, as much as it will for the prefent fuf- 

 tain, by adding gradually, fuppofe a few grains daily, 

 it will at length acquire the power of attracting near 

 double the weight which it would have attracted at 

 firft. It is probable, however, from what was for- 

 merly remarked, that this power has a limit. 



If a piece of iron, feme what more ponderous -than 

 a magnet will fufiain, is applied to the pole of the mag- 

 net, it is plain that on removing the hand the iron 

 muft fall. But if another piece of iron is held at fome 

 little diftance btlow the firft, the magnet will be able 

 to fupport it. The reaibn is, that both pieces of iron 

 being rendered magnetic, the fiiil piece is actually con- 

 verted into an artificial, magnet, by its contact with the 

 original, and its virtue is ihcreafed by the fecond piece 



* Cav. .f Adams on Mag. 398. J Car. 25. 



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