THE VARIATION OF ANGLES OBSERVED IN CRYSTALS. 
479 
At 11.45 P.M., ^ = 18°, the crystal was covered with etched triangles. 
At 12.0 (midnight), ^ = 17°, the etched figures were disappearing and w gave a good 
reading at 29° 54'. 
At 12.30 A. M., t — 154°, the faces were quite smooth. 
Theoretical Readings (from the angles 
Oy, 
139° 34', 
0 = 139° 234', 
oo, = 0° lof'. 
139° 18', 
30° O', 
w = 29° 55', 
= 0 ° 94 ', 
29° 454', 
o'y 
319° 3G', 
o' = 319° 24', 
o'o', = 0° 12', 
319° 18'. 
t = 
15-2°. 
"y 
29° 42-4', 
o'y 
319° 384', 
/ 
319° 174', 
o' = 319° 244', 
o'o', = 0° 14', 
t = 
= 14-9° 
30° 3', 
w = 29° 534', 
=r u° 19', 
"y 
29° 344', 
319° 404', o' = 319° 24|-', o'o' = 0° IG', 
_o'„, 319° IGi'. 
At 1.20 A.M. ; t = 14-9°. 
\ 139° 351', 
o,, 139° IGi', 
c.,3 30° 94', 
319° 154', 
o = 139° 22-4', = 0° 134'. 
The solution was then withdrawn. 
