•508 Mr. C. Scott Grarrett on the Infra-red and 



Table III. — Absorption of Sulphur Dioxide in the 

 Intermediate Region. 



Wave-lengths in 



o 



Angstroms. 



Wave 



Numbers. 



Wave-number 

 Differences. 



2789 



2780 



2764 



2757 



2734 



2719 



2685 



2669 



2661 



2652 



2621 



2614 



2594 



2582 



2572 



2554 . 



2537 



2497 



2464 



2456 



2427 



3586 

 3597 

 3618 

 3627 

 3657 

 3677 

 3725 

 3746 

 3758 

 3772 

 3815 

 3825 

 3854 

 3873 

 3889 

 3915 

 3942 

 4006 

 4058 

 4071 

 4121 



11(3) 

 21(1) 

 9(3) 

 30(2) 

 20(1) 

 48(2)+(3) 

 21(2) 

 12 (1) 

 14(1) 

 43(2)x(2) 

 10(1) 

 29(2) 

 19(1) 

 16(3) 

 26(1) 

 27(1) 

 64(l)+(2) 

 52(2)-f(3) 

 13(1) 

 50 (2) + (3) 



Mean of all differences (I) = 224. 



(2) -34-4. 

 (3) = 12-6. 



It would seem obvious from the above tables that the 

 whole absorption region in reality consists of two principal 

 band groups, the centre of one of which lies near X = 2960, 

 while the centre of the other lies beyond \ = 2107 which is 

 the working limit of the spectrograph. In the first of these 

 bands there is a constant difference between the wave- 

 numbers of the centres of the sub-groups of 22*4 and in 

 the second band there is a mean constant difference of 34'4. 

 As regards the less refrangible band, although in Table II. 

 five band groups have been given with a molecular extinc- 

 tion coefficient of 402*2, the trace of the absorption curve 



