MR. R. T. GLAZEBROOK ON PLANE WAVES IN A BIAXAL CRYSTAL. 371 
Table XII. 
a . 
0. 
ri 
Final Theory. 
r-2 
Experiment. 
Difference. 
16 
48 
1-66304 
1-66300 
4 
22 
66 
1-64608 
P64603 
5 
25 
75 
1-62822 
1-62807 
15 
26 
78 
1-58354 
1-58365 
-11 
16 
48 
1-55268 
1-55157 
11 
7- 
d. 
0 2 
Final Theory. 
02 
Experiment. 
Difference. 
10 
30 
1-68467 
1-68448 
19 
9 
27 
1-68464 
1-68452 
12 
11 
33 
1-68470 
1-68447 
23 
11 
33 
1-68472 
1-68457 
15 
12 
36 
1-68475 
1-68452 
23 
Column a gives the change in /x, 1 clue to a change of 10' in C L. 
Column /3 gives three times that change which, assuming the theory of proportional 
parts, will be the change in /y clue to a change of 30' in C L. 
Subtracting this from the values of fx l given by the original theory, we get the final 
theoretical values of /x,. These agree much more closely with experiment than the 
original values. 
But the effect of this further change will be to over correct /x 2 . 
The first change has reduced the differences for /x 3 by the amounts given by y, 
Table XII. 
Multiplying these by 3 we get S, the changes produced in /x 3 by a change of 30' 
in C L, and adding these values to the original theoretical values of /x 2 we get the 
final theory, which differs from experiment by rather more than the original theory 
and in the other direction. 
Thus an increase of C L will not, on the whole, produce the required effect. 
Similarly a decrease will not produce it either. 
Section IX .—Possibility of an Error in the Positions of the Faces discussed. 
We have seen, however, that by increasing L P by 17' 5" and A L P by 1°, we can 
make the agreement between theory and experiment extremely close. 
This alteration in the values of L P and ALP may be effected in two ways. 
We may suppose either that, the axes of elasticity retaining their position with 
3 b 2 
