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LXII. The Ultra-violet Absorption System of Sulphur Di- 

 oxide. _% E. C. C. Baly, M.Sc., F.R.S., Grant Professor 

 of the University of Liverpool, and C. S. GrARKETT, B.Sc* 



IT was shown in the preceding paper that the ultra- violet 

 absorption band group of gaseous sulphur dioxide can 

 be resolved into a series o£ sub-groups and that constant 

 differences exist between the wave-numbers of the centres 

 or heads of the sub-groups. 



The whole region over which absorption is exhibited can 

 be divided into three portions, namely, that between \ = 3182 

 and X — 2802 where there is a constant difference of 22*4 

 between the wave-numbers of twenty successive sub-groups,, 

 that between A, = 2324 and \ = 2107 where there is a constant 

 difference of about 34*1 between the Wave-numbers of 

 fourteen sub-groups, and the intermediate portion with 

 twenty-one sub-groups where both constant differences 

 occur together with a third difference of about 12. It was 

 further shown that these differences are compounded from 

 four basis constants, 0'2, 2'8, 4, and 4*3. Further, the 

 wave-numbers of the infra-red absorption bands of sulphur 

 dioxide can be expressed as multiples of 96*32, which is the 

 product of all four basis constants, while the product of 2*8 

 and 4 gives rise to the infra-red absorption of oxygen and 

 4*3 gives rise to the infra-red absorption of hydrogen 

 sulphide. 



Again, the wave-number of the centre of the less refran- 

 gible ultra-violet band of sulphur dioxide was shown to be 

 25 times that of the most important infra-red band of this 

 gas, namely, 96'32 X 14. 



Mention was also made of the accurate measurements by 

 Miss Lowater of the component absorption lines which are 

 associated together in the sub-groups |- Miss Lowater only 

 investigated the region between X=3118 and X = 2707; that 

 is to say, she only measured the component lines of the less 

 refrangible ultra-violet absorption band of sulphur dioxide. 

 She arranged the lines in 44 arbitrary series of constant 

 wave-number differences, and the mean of all 44 differences 

 was 22 -33. Although 42 lines were found not to fit in any 

 of her series, it is obvious that the same constant differences 

 occur between the individual absorption lines as was shown 

 in the preceding paper to exist between the heads of the 

 sub-groups. 



* Communicated by the Authors. 



t Astrophys. Journ. xxxi. p. 311 (1910). 



