MAGNETISM.* 59 



The Magnetic Power on the Surface. 



It has been discovered that the power of magnetic 

 attraction resides wholly in the surface of the iron 

 bodies, and is independent of the mass. An empty 

 bomb-shell will attract as strongly as a solid sphere of 

 the same material. 



Wedgervood's Black Ware. 



Wedge wood's black ware, which is made of basalt, 

 attracts the magnet strongly. 



Electricity and Magnetism.* 



Electricity affects all bodies, whether as passing 

 through them, or as being attached to their particles ; 

 on the contrary there are only a small number of 

 bodies, such as iron, steel, nickel and cobalt,fin which 

 distinct traces of magnetic action have been observed. 

 Hence it has become a question whether magnetism 

 be a peculiar fluid, found only in bodies susceptible 

 of its influence ; or, if it be merely a modification of 

 the electric fluid, distributed in a particular manner. 

 All that has hitherto been proved is, that magnetism 

 may be developed in different bodies by the action 

 of electricity, but the identity of the fluids has not 

 yet been proved, although the experiments of Mr. 

 Oersted has gone very far towards establishing this 

 fact. 



What has hitherto been considered as the magnet- 



* The controversy relative to the two hypotheses on which 

 electrical phenomena are explained, seems almost equally ba- 

 lanced, the scale rather inclining as yet to those who maintain the 

 existence of electricity and magnetism as two distinct fluids. 



t Since the above was written the experiments of M. Arago 

 and Mr. Barlow extend this property, of being affected by the 

 magnet under certain modifications, to all metallic substances, and 

 various other bodies, proved capable of receiving magnetic im- 

 pressions, though in a more evanescent manner than malleable 

 iron, and in an infinitely less intense degree. 



