350 MR. R. T. GLAZEBROOK ON PLANE WAVES IN A B1AXAL CRYSTAL. 
Table to determine the Value of 
■h 
D + i. 
r- 
1 
fi- 
O / II 
51 16 7 
101 47 15 
30 39 0 
•427076 
49 41 7 
101 48 45 
29 53 13 
•427061 
47 49 7 
101 57 45 
28 57 43 
•427049 
46 5 22 
102 13 0 
28 6 3 
•427039 
44 26 7 
102 34 45 
27 14 5 
■427029 
42 55 27 
103 3 5 
26 25 31 
•427018 
Substituting the values of \p' from this table in the formulae for cos 9 and cos 9' we 
can find 9 and 9'. 
The values of 9—9' are 
O 
/ 
// 
3 
31 
50 
3 
37 
30 
3 
42 
20 
3 
47 
50 
3 
52 
50 
3 
57 
40 
Substituting these values in the formula for /x,., the mean of the results agrees 
closely with 
fj. c = 1'53013 
Thus we may take 
/jl„= 1 "68560 
/x 4 = 1-6811 5 
^—1-53013 
And the angle between 0 C and the optic axes is 
9° 4' 5" .(5) 
If (f) is the angle as seen in air 
cf>= lA^lVKT' 
The value Kirchhoef found by experiment was 
15° 27' 
The close agreement is noteworthy. 
As in the first part, the agreement is much closer than it would be taking IIudberg s 
values of /x f/ , /x/„ /x ( .. 
