Prof. Challis on a Theory of the Dispersion of Light. 273 



from the values of /x and \ for Fraunhofer's lines B, E, H, which 

 would probably be the most favourable for obtaining results in 

 accordance with observation,, in order to put the theory to a 

 severer test I have calculated, first, with the data for the lines 

 B, E, G, and then with those for C, F, II . As the comparisons 

 in the two cases would necessarily be affected by errors in the 

 data, and as I had no reason to prefer one set of data to the 

 other, I have considered the mean between the values of \ given 

 by the two calculations to be a more correct expression of the 

 theoretical result than either value taken separately. 



By the preliminary calculations the constants A', B', C were 

 determined as follows : — 



Byl, log A' = 1*0703283, log B' = 0*3013700, C' = 7*161816. 

 By 2, log A' = 1-0604669, log B'= 0*2746509, C'=7*057775. 











Excess of calculated wave- 



Designa- 

 tion of 



Kirchhoff' s 



DUschei- 

 ner's refrac- 



Ditschei- 

 ner's wave- 





length. 











ray. 



measure. 



tive index. 



length. 



By first 

 calcula- 

 tion. 



Bysecond 

 calcula- 

 tion. 



Mean. 



B 



5930 



1-61358 



68833 







+ 117 



+ 58 



C 



694-0 



1-61537 



65711 



- 80 







- 40 





877-0 



1-61824 



61470 



-106 



- 66 



- 86 



D 



1004-8 



1-62020 



59021 



-100 



- 78 



- 89 





11350 



1-62166 



57193 



+ 92 



+ 104 



+ 98 





1207-5 



1-62274 



56240 



- 70 



- 64 



- 67 





12800 



1-62363 



55368 



- 64 



- 64 



- 64 





1324-8 



1-62415 



54854 



- 37 



- 39 



- 38 





1351-3 



1-62448 



54549 



- 34 



- 37 



- 35 





1389-6 



1-62494 



54132 



- 28 



- 33 



- 31 





1421-6 



1-62530 



53792 



- 3 



- 9 



- 6 



E 



1523-5 



1-62650 



52783 







- 11 



- 5 





1577-5 



1-62705 



52349 



- 7 



- 19 



- 13 





1634-0 



1-62760 



51912 



4- 2 



- 12 



- 5 





1648-8 



1-62775 



51809 



- 10 



- 24 



- 17 





1655-6 



1-62782 



51754 



- 8 



- 22 



- 15 





1693-8 



1-62817 



51503 



- 21 



- 36 



- 28 





1750-4 



1-62872 



51068 



+ 9 



- 8 



4- 1 





1777-4 



1-62897 



50879 



+ 17 







+ 8 





18340 



1-62953 



50493 



+ 5 



- 13 



- 4 





1885-8 



1-63003 



50145 



+ 8 



- 11 



- 2 





19200 



1-63038 



49914 



+ 1 



- 18 



- 8 





1961-0 



1-63075 



49653 



+ 15 



- 5 



+ 5 





1989-5 



1-63113 



49412 



+ 7 



- 13 



- 3 





2005 



1 63133 



49269 



+ 21 







4- 10 





2041 4 



1-63177 



4S990 



+ 19 



- 2 



+ 8 





2067-0 



1-63205 



48791 



+ 42 



+ 20 



+ 31 



F 



2080-1 



1-63225 



48687 



+ 22 







+ 11 





21198 



1-63269 



48317 



+ 122 



+ 100 



+ 111 





21871 



1-63390 



47717 



+ 7 



- 17 



- 5 



