Scientific Lectures. 175 



therefore these curves indicate the lines in which the directive force 

 of the magnet acts, or, as philosophers are pleased to state it, they 

 are the lines of resultants of the actions of the magnet, for the iron 

 filings which trace them, are, when under the inductive action of 

 the magnet, little magnets, and therefore they trace these lines exactly 

 as the tiny needle did in our previous experiments, when you saw it 

 always placing its length in the direction of a curve. But they indi- 

 cate more, far more, than this. That wonder of experimental fertility, 

 Faraday, in 1831,* made this remarkable discovery, probably the 

 most subtile and far-reaching insight yet made into the mysteries of 

 nature. He found that when a wire was closed on itself, forming 

 what we call a circuit — that is, a metallic path along which elec- 

 tricity can pass — he found that when such a wire was passed along 

 these curves, that is, without cutting any of them, that nothing 

 happened, no electricity flowed through the wire ; but, when this 

 wire cut across any of these curves, then a current of electricity 

 traversed the wire, going round and round as long as the wire was 

 moved so as to cut these lines. Also, when the wire was moved, 

 only in one and the same direction, then the electricity went in one 

 direction through the wire, but, when the motion was reversed, the 

 direction of the current was reversed also. 



By this wonderful discovery — the production of a current of elec- 

 tricity from a magnet — the name of Faraday will ever remain illus- 

 trious. He did many good things, but this excelled them all. With 

 a master's hand he traced the strong, broad outlines of the truth, and 

 forty years' philosophers have pondered on these facts and have made 

 thousands of experiments, yet have failed to fathom their full signifi- 

 cance. 



Faraday termed these curves " the lines of magnetic force," and 

 wrote much of them. Their contemplation constantly suggested and 

 directed his researches ; and one of his last papers was devoted to 

 calling the attention of philosophers to the deep insight which their 

 study would give into the manner of action of other radiant forces. 



Let us consider them with more minuteness. You observe that this 

 is the axis, or the center line of the magnet ; those lines run off in its 

 direction ; these appear to radiate or spread out, fan-shape, from its 

 end, and when traced back they all converge to a point on its centre 

 line, called its pole. While these, which are further removed from the 

 axis, curve slightly in their upward or downward path, those nearer 



* Faraday, Exp. Resear. in Electr., London, 1849 ; vol. i, p. 7. Royal Society, Trans., 1832. PhU 

 Trans., 1852. 



