104 



parallel to each other, giving as effect a torsion of the symmetry 

 DOQ ox CQO as a result. In accordance with the fact that these 

 relations between the three groups are reciprocal, a magnetised 

 steel-wire if twisted by a force at both its ends, will show a diffe- 

 rence of potential (current) produced in it, the presence of which 



can be easily demonstrated by the 

 induction-current it produces in an 

 encircling solenoid. Here also the super- 

 position of the magnetic field (C**, ) and 

 the torsion (D^) or C^, will have a 

 result of the symmetry C^, and this 

 group CQO being a sub-group of C^ , the 

 occurrence of an electric current having 

 the latter symmetry, is compatible 

 with the superposition of both causes. 

 In the same way a soft iron rod 

 will become a magnet if an electric 

 current passes through it, while being 

 twisted by a force applied to one of 

 its ends; the other end is held fast. 

 This phenomenon also can easily be 

 demonstrated by means of the induction- 

 current the magnet will produce in an 

 encircling solenoid. It is a fact worthy 

 of attention that the free electrons of 

 the iron rod, moved by the electric force, 

 are not the same as the electrons which 

 are attached to the iron-atoms them- 

 selves, and whose motion is the cause 

 of Ampere's "molecular currents". 

 The kinetic energy of both kinds of electrons in the metal must 

 therefore be interchanged to and fro in some way or other, because 

 in experiments like these, there must evidently exist definite con- 

 nections between them. 



16. French authors especially 1 ) have frequently pointed to 

 the fact that for the description of physical relations, it often is 

 more desirable to bring to the fore the absence of some symmetry- 



!) Vid. i. a.: L. Pasteur, Deux Legons sur la Dissymttrie Moleculaire, 

 professees devant la Societe Chimique de Paris (1860); P. Curie, Journal de 

 Physique, (3). 3. 407. (1894). 



Fig. 98. 



