620 ALDITIONS. 



rally found to be connected, 6 and have illustrated this law in the case 

 of electrical, magnetical, and chemical polarities. If we regard mo- 

 tion backwards and forwards, to the right and the left, and the like, as 

 polar relations, we see that magneto-electric induction gives us a new 

 manifestation of connected polarities. 



Diamagnetic Polarity. 



But the manifestation of co-existent polarities which, are brought 

 into view in this most curious department of nature is not yet exhaust- 

 ed by those which we have described. I have already spoken (chap. 

 iv.) of Dr. Faraday's discovery that there are diamagnetic as well as 

 magnetic bodies ; bodies which are repelled by the pole of a magnet, 

 as well as bodies which are attracted. Here is a new opposition of 

 properties. What is the exact definition of this opposition in con- 

 nexion with other polarities ? To this, at present, different philoso- 

 phers give different answers. Some say that diamagnetism is com- 

 pletely the opposite of ordinary magnetism, or, as Dr. Faraday has 

 termed it for the sake of distinction, of paramagnetism. They say that 

 as a north pole of a magnet gives to the neighboring extremity of a 

 piece of soft iron a south pole, so it gives to the neighboring extremi- 

 ty of a piece of bismuth a north pole, and that the bismuth becomes 

 for the time an inverted magnet ; and hence, arranges itself across the 

 line of magnetised force, instead of along it. Dr. Faraday himself at 

 first adopted this view ;" but he now conceives that the bismuth is not 

 made polar, but is simply repelled by the magnet; and that the 

 transverse position which it assumes, arises merely from its elongated 

 form, each, end trying to recede as far as possible from the repulsive 

 pole of the magnet. 



Several philosophers of great eminence, however, who have 

 examined the subject with great care, adhere to Dr. Faraday's first 

 view of the nature of Diamagnetism as W. Weber, 7 Pliicker, and 



o 



Mr. Tyndall among ourselves. If we translate this view into the lan- 

 guage of Ampere's theory, it comes to this : that as currents are 

 induced in iron and magnetics parallel to those existing in the inducing 

 magnet or battery wire ; so in bismuth, heavy glass, and other diamag- 

 netic bodies, the currents induced are in the contrary directions : 



6 Phil. Ind. Sc. B. v. c. ii. Faraday's Researches, Art. 2429, 2430. 



7 Poargeudorfs Ann. Jou. 1848. 



