THE BEGINNINGS OF LIFE. 13 



By the rubbing of substances of a different nature 

 together electricity is produced, as in the ordinary 

 electrical machine. Magnetism, again, may result from 

 motion; either immediately, in a bar of soft iron, 

 through a repetition of percussions, which, producing 

 motion amongst the particles of the bar, facilitate their 

 assumption of the magnetic mode of collocation; or 

 mediately through the intervention of electricity which 

 lias itself been generated by motion. And, as Mr. Her- 

 bert Spencer says 1 , c The transformations of electricity 

 into other modes of force are still more clearly demon- 

 strable. Produced by the motions of heterogeneous 

 bodies in contact, electricity, through attractions and 

 repulsions, will immediately reproduce motion in neigh- 

 bouring bodies. Now a current of electricity generates 

 magnetism in a bar of soft iron ; and now the rotation 

 of a permanent magnet generates currents of elec- 

 tricity. Here we have a battery in which, from the 

 play of chemical affinities, an electric current results; 

 and there, in the adjacent cell, we have an electric 

 current effecting chemical decomposition. In the con- 

 ducting wire we witness the transformation of elec- 

 tricity into heat ; while in the electric sparks and in 

 the voltaic arc we see light produced That mag- 

 netism produces motion is the ordinary evidence we 

 have of its existence. In the magneto-electric machine 

 we see a rotating magnet evolving electricity. And 



1 ' First Principles,' p. 254. 



