300 



ELEMENTARY LESSONS ON [CHAP. v. 



LESSON XXVI 1 1 . Diamagnetism. 



339. Diamagnetic Experiments. In 1778 

 Brugmans of Leyden observed that when a lump of 

 bismuth was held near either pole of a magnet needle it 

 repelled it. In 1827 Le Baillif and Becquerel observed 

 that the metal antimony also could repel and be repelled 

 by the pole of a magnet. In 1845 Faraday, using power- 

 ful electromagnets, examined the magnetic properties 

 of a large number of substances, and found that whilst a 

 great many are, like iron, attracted to a magnet, others 

 are feebly repelled. To distinguish between these two 

 classes of bodies, he termed those which are attracted 

 paramagnetic, 1 and those which are repelled diamag- 

 netic. Tile property of being thus repelled from a magnet 

 he termed diamagnetism. 



Faraday's method of experiment consisted in suspend- 

 ing a small bar of the substance in a powerful magnetic 

 field between the two poles of 

 an electromagnet, and observing 

 whether the small bar was at- 

 tracted into an axial position, as 

 in Fig. 126, with its length along 

 the line joining the two poles, or 

 whether it was repelled into an 

 equatorial position, at right 

 angles to the line joining the poles, 

 across the lines of force of the 

 field, as is shown by the position 

 of the small bar in Fig 127, sus- 

 pended between the poles of an electromagnet con- 

 structed on RuhmkorfFs pattern. 



1 Or simply " magnetic." Some authorities use the term " ferro- 

 magnetic." SieUro-mttgaetic would be less objectionable than this hybrid 

 word. 



Fig. 126. 



