209 ^i 



Proceedings of the Royal Institution of Great Britain. 



The Evening Meetings of the members of this Institution were 

 resumed on 



Friday, January 26ihy 



when Mr. Faraday gave " A General Account, accompanied with 

 experimental ilhistrations, of the late Extension of our Know- 

 ledge relative to Magnetism, founded on the discovery of M. Arago, 

 of the effects of metal when in motion." 



The magnetic phenomena with which we were acquainted prior 

 to the year 1818, consisted of the various effects produced by 

 the action of natural and artificial magnets upon each other, and 

 upon the metals iron and nickel, with some effects, very feeble 

 and uncertain, (as to their origin), produced by the mutual 

 action of magnets and bodies in general. In the year 1819, 

 Oersted discovered that a current of electricity produced magnetic 

 effects of an extraordinary kind. Upon the extension of the dis- 

 covery by himself and others, it was found that the current 

 was able to influence the magnetic needle, and permanently to 

 magnetize steel bars, but that the power was disposed in a manner 

 entirely unknown till then, and best expressed by the term, first 

 applied to it by Dr. Wollaston, of Vertiginous Magnetism. In the 

 year 1821, Seebeck first discovered such an arrangement of matter, 

 that a metallic ring could be made vertiginously magnetic in 

 every part, in a manner so analogous to that occasioned by a 

 current of electricity, that though no other evidence of the elec- 

 tricity could be obtained than the existence of the magnetism, still 

 it was generally admitted to be sufficient, and the dependance 

 of the latter upon the former inferred. It was in 1824, that 

 M. Arago added an entirely new fact to this branch of knowledge, 

 by showing, that when a magnet was brought near a plate or ring 

 of copper, or other substance not usually considered magnetic, and 

 the one made to assume a rotary motion, that it immediately 

 exerted a powerful influence on the other, which it had not whilst 

 in a state of rest, and either tended to make it move, or was 

 itself retarded. The effect was shown by making magnets and 

 plates revolve or vibrate near each other. A horse-shoe magnet, 

 weighing several pounds, was made to rotate rapidly by a thin 

 copper plate ; and a circular copper plate, which, being suspended 

 according to Mr. Sturgeons method, by an axis not in the centre 

 of gravity, would vibrate, when moved, 60 or 70 times before it ac- 

 quired a state of test, would not vibrate more than six times when 



JAN.— MARCH, 1827. P 



