1898-99.] Lord Kelvin on Sellmeier’s Theory, 531 
X 
f 1 
i-(* 
ix positive. 
-Y 
i+i/ 
fx negative. 
-1*0 
*894 
- ’9 
•882 
- *8 
•866 
- 7 
*845 
•993 
-141-9 
-'6 
*816 
•988 
-82-3 
- -5 
•774 
•984 
-61-5 
- *4 
•707 
•971 
-33-5 
-•3 
•577 
•928 
-12*9 
- -2 
o- 
0 
0 
- -1 
imaginary 
imaginary 
imaginary 
- *0 
00 
0 
0 
+ •1 
1-732 
•928 
-12*9 
+ -2 
1-414 
•971 
-33-5 
+ •3 
1*291 
•984 
-61-5 
+ •4 
1-247 
■988 
-82-3 
+ *5 
1-183 
•993 
-141-9 
+ •6 
1-155 
+ 7 
1*134 
+ •8 
1*118 
+ •9 
1-105 
+ 1*0 
1-095 
by others. It is also interesting to remark that according to 
Sellmeier as now interpreted, the broadening of a single un- 
disturbed dark line, produced by increased density of the gas 
or vapour, is essentially on the high side of the finest dark line 
shown with the least density, and is in simple proportion to the 
density of the gas. 
