1898-99.] 
Lord Kelvin on Sellmeier’s Theory. 
527 
similarly the value of 1 — - for ra= '001, or density of vapour five 
times that in the case represented by fig. 1. Figs. 3 and 4 repre- 
sent the ratio of intensities of transmitted to normally incident light 
for the densities corresponding to figs. 1 and 2 ; and fig. 5 represents 
the ratio for the density corresponding to the value m = *003. The 
Fig. 3. m— -0002. 
| 
1 i-o 1 
f 0, 
1 
r 
3 
C-i 
I ; 
i 
L 
998 999 Dg 1000 D, 1001 1002 
Fig. 4. m= ‘001. 
— — , 
J 
r_ 
v ' 
1 
or 
V 
A 
99 
8 
93 
□ 
10 
boro, io 
01 
10 
02 
A 
Fig. 5. m—' 003. 
S96 997 998 999 D t 1000 °i 1001 1002 
following table gives the breadths of the dark bands for densities 
of vapour corresponding to values of m from ‘0002 to fifteen times 
that value ; and fig. 6 represents graphically the breadths of the 
dark bands and their positions relatively to the bright lines D 1? D 2 
for the first five values of m in the table. 
Values of m. 
Breadths of Bands. 
Di. 
d 2 . 
•0002 
•09 
•11 
•0006 
•217 
•383 
*0010 
•293 
•707 
•0014 
•340 
1-060 
•0018 
•371 
1-429 
•0022 
•392 
1-808 
■0026 
•408 
. 2-192 
•0030 
•419 
2*581 
