334 Mr. T. P. Dale on the Index of Refraction and 

 Table I. — Langley's Flint-glass Peism. 



Line. 



Wave-length. 



Index. 



9 from sin. 



9 from arc. 



9 from sin. 



9 from arc. 







0-34400 



1-6266 



28 21 6 



28 22 50 



29 16 30 



29 17 10 



H ... 



0-39679 



1-6070 



24 18 40 



do. 



25 5 





F 



0-48606 



1-5899 



19 38 10 



19 38 7 



20 14 50 



20 15 33 



D 



58890 



1-5798 



16 6 20 



16 6 26 











0-65618 



1-5757 



14 24 57 



14 24 57 



14 51 15 



14 52 25 



A 



0-76009 



1-5714 



12 24 20 



12 24 20 









0815 



1-5697 



11 33 46 



11 33 42 









0-850 



1-5687 



11 4 50 



11 4 43 









0-890 



1-5678 



10 34 30 



10 34 28 









0-910 



1-5674 



10 20 30 



10 20 23 









0-940 



1-5668 



10 21 



10 21 









1-130 



1-5636 



8 18 43 



8 18 23 









1-270 



1-5616 



7 23 19 



7 22 53 









1-360 



1-5604 



6 53 56 



6 53 15 









1-540 



1-5576 



6 9 30 



6 8 31 



6 20 30 



6 20 13 





1-580 



1-5572 



5 56 



5 54 20 









1-810 



1-5544 



5 10 40 



5 9 10 



5 19 50 



5 19 7 





1-870 



1-5535 



5 40 



4 59 10 









1-980 



1-5520 



4 43 55 



4 42 20 









2030 



1-5515 



4 37 11 



4 35 17 



4 44 32 



4 41 1 



Table II. — Rock-salt Prism. 



(Prof. Langley's Determinations, Phil. Ma^ 



May 1886, no. 132.) 





I. Wave- 

 length. 



Index. 



9 from 

 sine. 



9 from 

 arc. 



Differ- 

 ence. 



Limit of Eefract. 



Sine. 



Arc. 



M ... 

 L 



it:: 



G- ... 

 F 



b, ... 

 b, ... 



85 ::: 



c: 



B 



A 



p ... 



f 



* 



Q 



03727 



3820 



0-3933 



0-3968 



0-4303 



0-4861 



0-5167 



0-5183 



0-5889 



05895 



0-6562 



0-6867 



07601 



0-94 



1-13 



1-38 



1-82 



1-57486 



1-57207 



1-56920 



1-56833 



1-56133 



1-55323 



1-54991 



1-54975 



154418 



1-54414 



1-54051 



1-539 19 



1-53670 



1-5328 



1-5305 



1-5287 



1-526S 



24 46 35 



24 8 5 



23 23 50 



23 10 49 



21 17 



18 44 47 



17 35 41 



17 32 19 



15 22 49 



15 21 50 



13 46 12 



12 8 49 



11 51 12 



9 33 53 



7 56 42 



6 29 49 



4 55 24 



24 46 45 

 24 8 19 

 23 24 8 



datum. 

 21 17 7 

 18 44 47 

 17 35 40 

 17 32 16 

 15 22 49 

 15 21 52 

 13 46 12 

 12 8 50 

 11 51 13 

 9 33 58 

 7 56 40 

 6 29 51 

 4 55 14 



+6 10 

 14 

 18 



7 







-0 1 



-0 3 







+0 2 







+0 1 



+0 1 



+0 5 



-0 2 



4-0 2 



-0 10 



1-52570 

 1-5251 



1-5249 



H[ is found from indices of Hj and A, aud from H all the other lines are 

 deduced. Molecular distance h = - 032570 ; ju h — 3(^f — /xb) = 1-52621. 



