144 CORRELATION OF PHYSICAL FORCES. 



be stationary, conducting bodies moved across any of the 

 lines of magnetic force, i. e. lines in the direction of which 

 the mutual action of the poles of the magnet would place 

 minute portions of iron, have currents of electricity devel- 

 oped in them, the direction of which is dependent upon that 

 of the motion of the substance with reference to the magnetic 

 poles. Thus, as bodies affected by an electrical current are 

 definitely moved by a magnet in proximity to them, so con- 

 versely bodies moved near a magnet have an electrical cur- 

 rent developed in them. Magnetism can, then, through the 

 medium of electricity, produce heat, light, and chemical affin- 

 ity. Motion it can directly produce under the above condi- 

 tions ; i. e. a magnet being itself moved will move other fer- 

 reous bodies : these will acquire a static condition of equilib- 

 rium, and be again moved when the magnet is also moved. 

 By motion or arrested motion only, could the phenomena of 

 magnetism ever have become known to us. A magnet, how- 

 ever powerful, might rest for ever unnoticed and unknown, 

 unless it were moved near to iron, or iron moved near to it, 

 so as to come within the sphere of its attraction. 



But even with other than either magnetic or electrified 

 substances, all bodies will be moved when placed near the 

 poles of very powerful magnets some taking a position ax- 

 ially, or in the line from pole to pole of the magnet ; others 

 equatorially, or in a direction transverse to that line the 

 former being attracted, the latter apparently repelled, by the 

 poles of the magnet. These effects, according to the views 

 of Faraday, show a generic difference between the two 

 classes of bodies, magnetics and diamagnetics ; according to 

 others, a difference of degree or a resultant of magnetic ac- 

 tion ; the less magnetic substance being forced into a trans- 

 verse position by the magnetisation of the more magnetic 

 medium which surrounds it. 



According to the view given above, magnetism may be 

 produced by the other forces, just as the vanes in the instance 



