20 



Mr. W. H. M, Christie on the 



[Mar. i, 



The dispersion is simply the difference between corresponding quan- 

 tities in the two columns and xa« 



The magnifying-power (given in the last two columns for H and A) in 

 this and following Tables is to be understood as that of a half -prism 

 haying X' (or yj/) for its refracting angle. 



Flint to Croivn. 



Dispersion and Magnifying-power. 



.f.' 



y • 





./. 



y A • 







fX 1 „ COS if/' 



fi' „_cos-4/' 



- % = 7- • 



{J. COS i// H 



COS l//A 



o 



45 



O 1 



55 6 



O J 



53 2 



2 







4 



1-24 



148 



47 



58 1 



55 44 



2 



17 



1-29 



1-21 



49 



61 6 



58 31 



2 



35 



1-36 



1-26 



51 



64 21 



61 26 



2 



55 



1-45 



1-32 



53 



67 52 



64 29 



3 



23 



1-60 



1-39 



55 



71 50 



67 46 



4 



4 



1-84 



1-52 



56 



74 5 



69 32 



4 



33 



2-04 



1-60 



57 



76 35 



71 23 



5 



12 



2-35 



1-71 



57| 



78 3 



72 22 



5 



41 



2-60 



1-77 



58 



79 38 



73 24 



6 



14 



2-95 



1-86 



58§ 



81 30 



74 28 



7 



2 



3-53 



1-95 



59 



83 53 



75 37 



8 



16 



4-82 



2-07 



59i 



88 10 



76 49 



11 



21 



15-86 



2-23 



Light Eeflected. 



Polarized 



in plane 

 of incidence. 



in perpendicular 

 plane. 



Total. 



45 

 49 



53 

 55 

 56 

 57 

 58 

 59 



59J 



per cent. 

 3-2 

 5-0 

 f H 8-9 

 \A 5-0 

 J H 13-1 

 | A 6-9 

 f H 16-4 

 ( A 8-3 

 J H 21-4 

 \ A 10-0 

 J H 29-9 

 { A 12-5 

 f H 48-6 

 [ A 16-1 

 J H 80-4 

 1 A 18-6 



per cent. 

 O'l 



0- 6 

 2-5 



1- 1 

 54 



2- 1 



7- 6 



3- 

 11-5 



4- 1 

 18-9 



5- 9 

 37-5 



8- 6 

 74-6 

 10-7 



per cent. 



1- 6 



2- 8 

 5-7 



3- 1 

 9-1 



4- 5 

 12-0 



5- 7 

 16-5 



7-1 

 24-4 



9-2 

 43-1 

 12-4 

 74-5 

 14-7 



For the 



purpose of comparing the direct-vision and 



ordinary compound 



