640 HENRY A. ROWLAND 



The new fact of electro-magnetism interested him. Soon he found 

 that the turning of the needle, as found by Oersted, could be accounted 

 for by the attempt of the north pole tp revolve around the wire in one 

 direction and the south pole in the other. Not content with demon- 

 strating the theory, he invented some pieces of apparatus by which 

 this revolution could be realized, and every collection of physical appar- 

 atus now has them. The little wires or magnets hanging in the cups of 

 mercury are familiar to all, and form the first notable instance of a 

 continuous rotary motion produced by the electric current; it was the 

 first form of electro-magnetic motor so common in our day. But we 

 can not call this a great discovery, as the principles were very apparent. 



Eight or nine years now passed before Faraday gave anything of 

 importance to the world in the subject of electricity and magnetism. 



Seebeck discovered thermo-electricity. Ohm discovered the law con- 

 necting electro-motive force, resistance and current, and the whole 

 scientific world was alert to discover new facts. Faraday brooded on 

 the subject: the electric current produced magnetism, why should not 

 magnetism produce an electric current? At the present age of the 

 world we could answer this question at once, by aid of the great law of 

 the conservation of energy. But fifty-seven years ago it was unknown, 

 except in a very vague manner; the foreshadowing of this great law 

 soon came into the mind of Faraday, but at this period he could only 

 grope blindly in the dark. He knew that a piece of soft iron became 

 magnetic in the presence of a magnet, and that a conductor was electri- 

 fied by induction when near a charged body. Reasoning by analogy, 

 why should not a conducting circuit have a current generated in it in 

 the presence of a wire carrying a current? This was Faraday's reason- 

 ing, and he proceeded to test it by experiment. Winding two wires 

 side by side, on a cylinder of wood, he passed strong currents of elec- 

 tricity through one of them, and attached the other at its two ends 

 to a galvanometer.Kttf'he slightest permanent deflection was observed, 

 and many a man would have pronounced the experiment a failure. 

 But Faraday was not of that nature; he tried again and again, and 

 while bending over the galvanometer in a vain effort to see a slight 

 permanent deflection, he noticed a little jerk of the needle, almost too 

 small to be noticed. His attention was arrested by this curious action, 

 and he proceeded to investigate it. 



He found that this slight movement of the needle was in one direc- 

 tion on making the current, and the opposite direction on breaking it. 

 He substituted a helix, enclosing an unmagnetized needle for the gal- 



