292 On the Existence of a Magnetic Medium in Space. 



doubt but that each piece is acted on, and consequently reacts, 

 precisely as a piece of steel very feebly magnetized, with its mag- 

 netic axis reverse to that of a steel needle free to turn, substituted 

 for it, would do. Each piece of bismuth therefore acts as a little 

 magnet, having its polarity as marked in the diagram, would do. 

 Hence the magnetizing force by which the middle fragment is 

 influenced is less than if the two others were away (this being 

 such a force as would be produced by a north pole on the right- 

 hand side of the diagram, and a south pole on the left). It is 

 easily seen, similarly, that if the line joining the centres be per- 

 pendicular to the lines of force, the magnetizing force on the 

 space occupied by the middle fragment is increased. Corre- 

 sponding assertions are true for the terminal fragments, although 

 the disturbing effect will be less on them in each case than in 

 the middle one. Hence the dia- 

 magnetization of each will be en- 

 feebled in the former case and 

 enhanced in the latter, by the pre- 

 sence of the others. It follows, 

 according to theprincipleof super- n, 

 position of magnetizations, that 

 if the line of the row be placed 

 obliquely across the lines of force, the magnetic axis of each par- 

 ticle, instead of being exactly parallel to the lines of force, will 

 be a little inclined to them, in the angle between their direction 

 and the direction transverse to the bar. The magnets causing the 

 force of the field must act on the little diamagnets, each with its 

 axis thus rendered somewhat oblique, so as to produce on it a 

 statical couple (as shown by the arrow heads), and the resultant of 

 the couples thus acting on the fragments will, when all these are 

 placed on a frame, or rigidly connected, tend to turn the whole 

 mass in such a direction as to place the length of the bar along 

 the lines of force. Still, I repeat, this action, although demon- 

 strated with as much certainty as the parallelogram of forces, is 

 so excessively feeble as to be absolutely inappreciable. A frag- 

 ment of bismuth, of any shape whatever, held in any position 

 whatever in any kind of magnetic held, uniform or varying most 

 intensely, only exhibits the resultant action of couples on all its 

 small parts if crystalline, and of forces acting always according 

 to Faraday's law on them if the field in which it is placed be 

 non-uniform. Some phenomena that have been observed are 

 to be explained by the resultant of forces from places of stronger 

 to places of weaker intensity in the field, others by the resultant 

 of couples depending on crystalline structure, and others by the 

 resultant of such forces and couples coexisting; and none ob- 

 served depend at all on any other cause. 



I gave a very brief summary of these views (which I had ex- 



