[eadie-satterly] REFRx\CTIVE INDEX OF OXYGEN 71 



the supervision of Professor J. C. McLennan. Slightly different 

 values for the wave-lengths of the absorption bands than those 

 found by Liveing and Dewar, were obtained. 



The bands observed in the visible spectrum were: 



Livqing McLennan 



and and 



Dewar. Shaver. 



A.U. A.U. 



6305 6285 



5785 5800 



5350 5350 



4773 4816 

 4470 



3828 



An endeavour was made with the Jamin interferometer to detect 

 these absorption bands by means of the changes in the refractive 

 index of the gas in the immediate neighbourhood of the absorption 

 bands. 



Line A B left-hand Fig. 3 shows for sorrie particular pressure the 

 variation of n with X for a gas showing no absorption band. C D 

 shows the variation at a lower pressure. The vertical line p q indi- 

 cates the change of index for a particular X when the pressure drop 

 is made. This change of index is proportional to the number of 

 fringes passing the centre of the field of view. Table L indicates 

 the results obtained when the pressure drop was practically one 

 atmosphere. The number of fringes changes gradually as the X of 

 the light used is altered. 



The broken lines E F G H and K L M N show the curves for two 

 pressures when the gas has an absorption band at the position indi- 

 cated hy X y. It was thought that there may be a marked change 

 in the vertical distance between E F G H and KL M N as the absorp- 

 tion band was crossed. 



The interferometer tube described in the first part of the paper 

 was accordingly filled with oxygen at a pressure of 1475 Ibs./in.^ 

 Readings were taken for pressure changes of an atmosphere, for wave- 

 lengths right across the spectrum in a region which included the 

 wave-lengths of the three absorption bands found by Liveing and 

 Dewar, McLennan and Shaver, as stated above. These bands were 

 of wave-lengths 6285, 5800, 5350 Â.U. They were the only ones 

 in the region of visibility of the interferometer. At the pressure of 

 100 atmospheres, the 5800 band appeared as an extremely faint 

 narrow line; the 0285 band did not show up and the 5350 band was 



