( 356 ) 
As the intensity of light of the apparatus used (Rowland’s grating, 
then Michelson’s echelon) has increased, so the percentage of ordinary 
light, possibly present, has decreased. 
We must conclude, that the orbits of the equivalent electrons, in 
planes normal to the magnetic force, are with great approximation 
circles. Elliptic orbits, fortuitously 'distributed in planes normal to 
the field, need not be conjectured for the representation of the 
phenomena. 
Rather closely connected with the subject of this paper, are the 
latest investigations of Jean Becquerel *) and A. Dufour 2 ). Dufour 
obtained various new results concerning the banded emission spectra 
of the alkaline-earth fluorides and chlorides radiating in a magnetic 
field and in some cases observed incomplete circular polarization. 
Several absorption bands of xenotime and tysonite according to 
J. Becquerel also exhibited incomplete circular polarization in a 
longitudinal magnetic field. He showed, however, lately 8 ) that in 
the case of these crystals there is no real incomplete polarization, 
but that under the action of the magnetic field besides the principal 
components, others of slightly different wavelength, come into existence, 
which exhibit a polarization opposite to that of the principal lines. 
Physics. — 11 On photo- and electrochemical equilibria .” By Prof. A. 
Smits. (Communicated by Prof. J. D. van der Waals.) 
Already previously 4 ) I pointed out that if a dark or thermo- 
chemical equilibrium is exposed to the action of light or electrical 
energy, and the system is susceptible to these forms of energy, a 
new equilibrium will be established, which deviates from the thermo¬ 
dynamic equilibrium, or in other words which is thermic metastable. 
On that occasion the heterogeneous photochemical equilibria in 
the systems Ag 2 Cl—Cl 2 and S—CS 2 , and further the homogeneous 
photochemical equilibrium 2 SO s S0 3 -f 0 3 and the homogeneous 
electrochemical equilibrium 3 0, 2 0, were discussed, in which a 
photochemical dissociation equilibrium with HC1 was predicted. 
*) Jean Becquerel G. R. T. 146, p. 413. 1907. 
*) A. Dufour G. R. T. 146, p. 118 et p. 229. 1908. Journal de Physique Avril 
1909. 
*> Jean Becquerel. These Proc. p. 146. June 1909. Contribution a la connais- 
sance du phenomene de Zeeman dans les cristaux. See also supplement N°. 
Leyden communications. 
4 ) Inaugural Address. Amsterdam Dec. 9 th 1907. 
