606 
MR. R. T. GLAZEBROOK ON THE REFRACTION OF PLANE 
Table II. 
0. 
0'. 
0-90°. 
Rotation. 
1 
O / 11 
80 47 0 
70 59 0 
36 26 10 
34 40 10 
o / n 
0 33 20 
4 55 30 
o / II 
4 22 10 
2 
78 14 0 
69 29 0 
36 5 20 
34 18 0 
1 29 20 
5 54 10 
4 24 50 
3 
73 43 0 
66 6 20 
35 16 40 
33 22 30 
3 30 10 
7 47 50 
4 17 40 
4 
70 57 40 
63 57 50 
34 39 50 
32 43 0 
4 56 30 
9 11 50 
4 15 20 
5 
66 6 20 
59 51 50 
33 22 30 
31 21 30 
7 47 50 
11 58 10 
4 10 20 
6 
64 12 30 
58 9 30 
32 48 10 
30 44 20 
9 2 0 
13 11 50 
4 9 50 
7 
59 45 0 
54 8 30 
31 19 0 
29 11 10 
12 3 20 
16 9 30 
4 6 10 
8 
57 54 20 
52 24 30 
30 38 40 
28 28 30 
13 22 50 
17 28 10 
4 5 20 
9 
52 16 40 
47 1 40 
28 25 10 
26 7 10 
17 34 10 
21 35 50 
4 1 40 
10 
46 50 40 
41 30 50 
26 2 10 
23 30 10 
21 44 10 
25 50 0 
4 5 50 
11 
41 41 30 
36 4 10 
23 35 30 
20 45 0 
25 41 40 
29 54 20 
4 12 40 
12 
36 5 40 
30 18 50 
20 45 40 
17 40 50 
29 53 20 
34 0 10 
4 6 50 
13 
30 36 0 
24 25 0 
17 50 10 
14 24 10 
33 48 10 
37 54 20 
4 6 10 
14 
24 42 0 
17 45 0 
14 33 50 
10 34 10 
37 43 20 
41 54 30 
4 11 10 
The rotation produced by the cell was measured carefully by Fizeau’s method, and 
the mean of several observations in which the extreme difference was about 5' gave 
the value 4° 6' 15". 
Each of the numbers then in Table II., column 5, ought to be equal to 4° 6' 15", 
and this is evidently not the case. The differences begin by being too large, and 
allowing for the probable error of the experiment, they decrease fairly uniformly as 
the angle of incidence decreases until we reach an angle of incidence of about 52°. 
As the angle of incidence is still further decreased there is a tendency to increase 
in the values of the rotation given by the table. The value 4° 12' 40 , line 11, is 
