C , 6,1 rr ow fyonmay acquire Magnetic Pcibsr. 4/7 



magnetic power depends upon the texture of the fub- 

 ftance which retiins it. 



Every portion of iron is capable of retaining only 

 a certain degree of the magnetic virtue. If a ft ohg 

 magnet is applied to a frnall piece of fteel, the fteel, 

 while within the influence of the magnet, appears 

 powerfully magnetic ; but if the magnet is removed, 

 the power fubfides to a certain degree, which may- 

 be termed the point of faturation *. A number of 

 magnetic bars, however, may be joined together, fo 

 as to form an exceedingly ftrong compound mag- 

 net f. 



idly. Iron is rendered magnetic merely by being 

 kept a confiderable time in a ikuation perpendicular 

 to the furface of the earth j and in this hemifphere 

 the lower extremity will be the north pole, and of 

 confequence the contrary effect will take place- in the 

 fouthern hemifphere. This phenomenon alfo is ex- 

 plained from the magnetifrn of the earth, which com- 

 municates its power to ferrugintous bodies, though by 

 almoft imperceptible degrees. Old iron ba?s in win- 

 dows, &c. are frequently found to be ftrongly mag- 

 netic J. 



The moft advantageous fituation of the bar is how- 

 ever not directly perpendicular, but rather in the di- 

 rection of the dipping needle ; and indeed the mag- 

 netic virtue which it acquires feems to be in propor- 

 tion as it approaches that direction. Hard iron or 

 fteel acquires little or no magnetifrn from the earth, 

 on account of its greater infenfibility to the magnetic 

 influence ; but it is well known that iron hardens by 



* Cav. 02. f Ib. 



I Leewenhook mentions an iron crofs, which had acquired a 

 very ftrong polarity. Adams, 432. 



expofure 



