436 
MR. R. T. GLAZEBROOK ON DOUBLE REFRACTION 
Table IX. 
\ or X . 
0 . 
Prism I. Face P. 
32° 36' 23" 
32° 36' 23"-0' 
„ „ Q. 
11° 19' 57" 
^'-11° 19' 57" 
Prism III. ,, P. 
lo 
CM 
CM 
o 
GO 
CO 
38° 29' 25"+ 0' 
» » Q- 
82° 23' 22" 
82° 23' 22" -V' 
Prism IV. „ P. 
to 
°o 
to 
GO 
72° 8' 28"+ 0' 
„ Q- 
115° 59' 28" 
115° 59' 28"-y/ 
Tables X., XL, XII., and XIII. give the values of 9 calculated from these formulae 
from the values of <£' xJj' given in Tables I., II., III., IV., V., and VI. 
For prism II. we must calculate the value of 9 from the formula 
cos 9— cos SM cos NM + sin SM sin NM— cos ^ 
= cos SM{cos NM+ tan SM sin NM cos x] 
cos SM 
cos v 
cos (NM — v) 
if 
tan v— tan SM cos x 
Now we have from the triangle M Q K (fig. 3) 
sin MK= tan QK cot PML 
We know that 
QK=0° 25' 11" 
PML=0° 29' 41"*7 [Tables VII. and VIII.] 
.-. MK=57° 59' 23" . . . . 
cos AQ = cos AK cos KQ 
AQ = 41° O' 55" 
( 8 ) 
( 9 ) 
( 10 ) 
But 
.-. AK = 41° O'49" .(11) 
.-. AM=AK+MK=99° O' 12" 
AS=26° 15' 31" [From Section III. (7).] 
.-. SM=72° 44' 41" 
(12) 
