Propositions in the Theory of Magnetic Force. 247 



its magnetic axis reverse along the lines of force. For Faraday 

 has discovered, that a large class of natural substances in the 

 stated conditions experience no other action than a tendency from 

 places of stronger towards places of weaker force, quite irrespective 

 of the directions the lines of force may have, and he has called 

 such substances diamagnetics. 



Cor. 4. A diamagnetic, held by its centre of gravity but free 

 to turn about this point, must react upon other magnets with the 

 same forces as a steel or other magnet substituted in its place, 

 and held with its magnetic axis reverse along the lines of force 

 due to all the magnets in its neighbourhood. 



Cor. 5. Any one of a row of balls or cubes of diamagnetic 

 substance held in a magnetic field with the line joining their 

 centres along a line of force, is in a locality of less intense force 

 than it would be if the others were removed ; but any one ball 

 or cube of the row, if held with the line joining their centres 

 perpendicularly across the line of force, is in a locality of more 

 intense force than it would be if the others were removed. 



Cor. 6. When a row of balls or cubes, or a bar, of perfectly 

 non-crystalline diamagnetic substance, is held obliquely across 

 the lines of force in a magnetic field, the magnetic axis of each 

 ball or cube, or of every small part of the substance, is nearly in 

 the direction of the lines of force, but slightly inclined from this 

 direction towards the direction perpendicular to the length of the 

 row or bar. Hence, since the magnetic axis of every part differs 

 only a little from being exactly reverse along the lines of force, 

 the direction of the resultant of the couples with which the mag- 

 nets, to which the field is due, act on the parts of the row or bar 

 must be such as to turn its length along the lines of force. 



Cor. 7. The positions of equilibrium of a row of balls or cubes 

 rigidly connected, or of a bar of perfectly non-crystalline dia- 

 magnetic substance, free to move about its centre of gravity in 

 a perfectly uniform field of force, arc either with the length along 

 or with the length perpendicularly across the lines of force : 

 positions with the length along the lines of force are stable; 

 positions with the length perpendicularly across the lines of force 

 are unstable. 



Cor. 8. The mutual influence and its effects, referred to in 

 Cors. 5, 6, 7, is so excessively minute, that it cannot possibly 

 have been sensibly concerned in any phamomena that have yet 

 been observed; and it is probable that it may always remain 

 inscnsiljle, even to experiments especially directed to test it. 

 For the influence of the most powerful electro-magnets induces 

 the peculiar magnetic condition of which diamagnetics are 

 capable, t<> bo slight a degree as to give rise to only very feeble, 

 scarcely sensible, mutual force between the diamagnetic and the 



