DIAMAGNETISM. i>53 



that magnetic bodies in the form of bars or needles, if free to move, 

 arrange themselves in the axial line joining the poles ; diamagnetic 

 bodies under the same circumstances arrange themselves in an equato- 

 rial position, perpendicular to the a:iial line. And this tendency lit 

 conceives to be the result of one more general ; that whereas magnetic 

 bodies are attracted to the poles of a magnet, diamagnetic bodies are 

 repelled from the poles. The list of diamagnetic bodies includes all 

 kinds of substances ; not only metals, as antimony, bismuth, gold, silver, 

 lead, tin, zinc, but many crystals, glass, phosphorus, sulphur, sugar, gum, 

 wood, ivory ; and even flesh and fruit. 



It appears that M. le Bailli had shown, in 1829, that both bismuth 

 and antimony and bismuth repelled the magnetic needle ; and as Dr. 

 Faraday remarks, it is astonishing that such an experiment should 

 have remained so long without further results. M. Becquerel in 1827 

 observed, and quoted Coulomb as having also observed, that a needle 

 of wood under certain conditions pointed across the magnetic curves ; 

 and also stated that he had found a needle of wood place itself parallel 

 to the wires of a galvanometer. This he referred to a magnetism 

 transverse to the length. But he does not refer the phenomena to 

 elementary repulsive action, nor show that they are common to an 

 immense class of bodies, nor distinguish this diamagnetic from the 

 magnetic class, as Faraday has taught us to do. 



I do not dwell upon the peculiar phenomena of copper which, in 

 the same series of researches, are traced by Dr. Faraday to the com- 

 bined effect of its diamagnetic character, and the electric currents 

 excited in it by the electro-magnet; nor to the optical phenomena 

 manifested by certain transparent diamagnetic substances under electrio 

 action ; as already stated in Book ix. 6 ] 



CHAPTER VIII. 



DISCOVERY OF THE LAWS OF MAGNETO-ELECTRIC INDUCTION. FARA- 

 DAY. 



I 



IT was clearly established by Ampere, as we have seen that mag- 

 netic action is a peculiar form of electromotive actions, and that, in 



8 See the Twentieth Series oj* Experimental Researches in Electricity, read tc 

 Mie Royal Society, Dec. 18, 1845. 



