[DAWES] ROTATORY DISPERSION OF QUARTZ 15 
7-1083 x ‘lyon es 0-1477 x 10 TE (Boltzmann). 
Be 
(a) x2 At 
—6 
8-0403 x 10 (Stefan). 
nn 
The following table illustrates the variation from the observed 
values of the values calculated by means of these formulæ:— 
(b) R=—1-581+ 
a ROTATION 
Wave-length = ue 
x10’mms. Observed Formula a Formula b 
SOUDE ET MEN Per 11-38 11-46 10-98 
BOOS LR eee oe 15-20 15-13 14-83 
GOOOR Seale ose ree 20-75 20-88 20-75 
SOOO REPAS ENTREE ART 30-82 30-54 30-58 
ADODRSE Norra wee 50-50 50-19 48-67 
OOO Mote MIRE RD ane 68-40 67-86 64-05 
SOOO ees oes 98-6 97 -23 87-75 
D2 DOO RAE eae Ae 154-2 151-53 127-07 
POOR are Ur 249-0 237-16 180-77 
The two constant formula developed by Drude from a considera- 
tion of the action of free electrons in the quartz on the light waves 
passing through a plate, viz.: 
—6 
2.9 5 . (0). 
p—/12:200 __5:046|,, 
1 Te 2 f 
seems to give almost perfect agreement over the whole range of wave 
lengths. (A,, is the wave length corresponding to the set of free electrons 
whose periods are nearest to those of the light waves.) 
