60 A STUDY OF THE ABSORPTION SPECTRA. 



For xenotine the following table is given: 



There does not seem to be any relation between the Zeeman effect and 

 the effect due to change in temperature. Becquerel also states that the 

 Zeeman effect is independent of the temperature. Related bands are 

 usually affected in the same way by change in temperature. 



In the introduction the ordinary equation of an electron considered 

 in the theory of dispersion was: 



m'x + kx + n 2 x = eE cos pt 



The resistance kx designates a mean resistance, and causes the decay 

 of the light vibration. It may result from sudden shocks undergone in 

 any irregular or fortuitous manner by any of the electrons taking part in 

 the absorption of light. The greater k is the wider the band will be. The 

 above equation leads to a value of the refractive index \i. 



[i 2 {1-k 2 )=\+Z 



e h d\d 2 -dl h ) 



(d 2 -dl h )+d 2 dl 2 



k is the coefficient of absorption; 2 it d 0h is the period corresponding to the 

 middle of an absorption band h; e h is a coefficient depending on the sub- 

 stance and the band. 



4xV 2 e 2 IN h dl h 



eh = 



m h 



Kh 



Nh is the number of electrons h/cc; d\ = d 2 0h . Becquerel has ob- 



m h 



tained the value of the ratio of d 1 at 20 and at 186. 

 those of tysonite. 



The bands are 



The ratios of d' are very nearly the same as the ratios of the square 

 roots of the absolute temperature. The width of the bands measured 



