WITH MAGNETISM AND ELECTRICITY. 179 



as the phaenoniena of interference served to decide the alterna- 

 tive between the theories of emission and of undulation ; and 

 this is the most essential and important character that can be 

 ascribed to the discovery of Faraday. Through the discovery 

 of diamagnetism the hypothesis of electric molecular currents in 

 the interior of bodies is corroborated; and the hypothesis of 

 magnetic fluids in the interior of bodies is refuted, — a result 

 which also finds a corroboration in the closer and more direct 

 examination of variable magnetism, namely, in the law accord- 

 ing to which the strength of the variable magnetism is deter- 

 mined from the magnitude of the magnetic or electro-magnetic 

 force ; this, however, deserves a closer discussion here. 



Dependence of the Variable Magnetism upon the Magnitude of 

 the Magnetic or Electro-magnetic separating Force. 



According to the foregoing theory of diamagnetism, the dia- 

 magnetic moment of a diamagnet is proportional to the magni- 

 tude of the magnetic or electro-magnetic separating force. Ac- 

 cording to the notion heretofore entertained regarding the 

 moveable magnetic fluids within the molecules of iron, the same 

 proportionality holds good for the magnetic moment of a vari- 

 able magnet. If, however, this notion, together with the hypo- 

 thesis of magnetic fluids in the interior of bodies, be rejected, 

 and instead of it Ampere's notion, that the molecules of iron are 

 the ponderable bearers of permanent molecular currents, be 

 assumed, from it will follow a different law of dependence 

 between the variable magnetism and the magnitude of the mag- 

 netic or electro-magnetic separating force. 



In Plate I., fig. 1, let NS be the axis of an unchangeable mo- 

 lecular current, which is capable of rotation around its centre C ; 

 when the magnetizing force X is =0, let the position of equi- 

 librium for this axis be parallel to ND. The fact that the mag- 

 netism excited in soft iron by the magnetizing force disappears 

 again of itself, as soon as the magnetizing force ceases to act, 

 proves that the molecular current, to the rotation of which the 

 excited magnetism is due, recedes of itself to its original position 

 parallel with ND. This force of recession, which is to be re- 

 ferred to the reciprocal actions of the iron particles, must 



