106 



field, - - with the exception of the single one just mentioned, - 

 will disappear, and now really all circumstances of symmetry (or 

 of Asymmetry) in the resulting cause will become such as to be 

 compatible with an eventual occurrence of the electric current (C, ) 

 as is observed in the Hall-effect. 



In the same way the motion of the string in Einthoven's string- 

 galvanometer, or that of the electric arc in the Birkel and- Ey de- 

 furnaces, will be symmetrical with respect to a plane passing through 

 the electrodes, or perpendicular to the lines of force of the mag- 

 netic field applied. 



However the magnitude of such a predicted or expected effect 

 must be investigated in every case by special experiments ; as already 

 stated, it may be too insignificant as to be detected by the usual 

 experimental methods. The general reasonings only teach us that, 

 if such an effect be produced by two superposed causes, the dis- 

 symmetries of the last are added to each other, and the symmetry 

 of the effect must be in accordance with the higher degree of dis- 

 symmetry (i. e. the lower symmetry) thus produced. 



The views concerning the symmetry or the dissymmetry of causes 

 and effects, are principally identical : but, in the one case is the chief 

 attention drawn to the symmetry-properties still present, in the 

 other case to the symmetry-properties which have disappeared. 



17. Finally it may be remarked that a number of problems 

 which can be answered only in the experimental way, are connected 

 with the views developed in the preceding paragraphs. 



If only the superposed physical conditions be such that an effect, 

 resulting from the interference of them may be expected with some 

 probability, it is worth trying such an experiment tentatively. 



Thus it may possibly be found that a difference of potential would 

 be observed with two electrodes plunged into a liquid of strong optical 

 rotatory power, if this fills a tube and be placed in a strong homo- 

 geneous magnetic field, having its lines of force parallel to the axis 

 of the tube and to the direction of an incident beam of polarised 

 light; and vice versa. 



If in a superposed magnetic and electrostatic field, with their 

 lines of force parallel to each other, a chemical reaction takes place, 

 in which a racemic acid or base combines with an inactive base or 

 acid, it might under favorable circumstances perhaps be observed 

 that the reaction-velocities of the dextro-, and laevogyratory com- 

 ponents of the racemic substance which combines with the inactive 



