338 
MR. R, T. GLAZEBROOK ON PLANE WAVES IN A BIAXAL CRYSTAL. 
All the angles 0 L , 9{, d. 2 , 67, and p, were observed several times throughout the 
work. 
The mean of the observations give 
=54° 17'6".(3) 
# 1 ' = 75° 16' 20". (4) 
0. 2 =88° 40' 35" .......... (5) 
0 3 ' = 88 ° 20 ' 20 ".. ( 6 ) 
p =31° 53' 30" .(7) 
In no case was the difference between the mean and any one of the observations so 
great as 20". 
Substituting these values we find 
a i =7l° 49' 30" 1 
^ = 60° 25' 49" J.( 10 ) 
a 2 = 90° 19' 10" I 
/3 2 =88° 14' 32" /. 
Also 
sin 3 y 1 = cos 2 a 1 + cos 2 /3 X 
sill 3 y 2 = COS 2 a 2 + cos 3 /5 2 
whence 
ri = 35° 42' 57".(12) 
77 —y 2 =l° 47' 11".(13) 
Let R O meet the sphere again in 11', and let the figure represent the sphere as seen 
by an eye on O C produced. 
Fi°\ 4. 
