(^'different Specks nfGlass^ 
RkfracI'ing 
Media. 
Temp. Reaum- I 
Spec. Gravity. 
Angle 
of the 
Prism. 
Angle 
of De- 
viation. 
BC 
CD 
DE 
EF 
FG 
GH 
Flint glass, 
No. 13. 
O 
15 
t— 
CO 
26° 24 30 
17° 2 7 S 
t u 
3 16 
/ // 
9 4.2 
1 1' 50" 
/ // 
10 33.9 
° 20 23!9 
o / // 
18 18 
Crown glass, 
No. 9. 
14 
2.535 
39 20 35 
22 3819 
2 44.5 
7 23.5 
9 14 
814 
1510 
13 18 
Water, - 
15 
1.000 
58 5 40 
22 36 40 
3 24 
8 10 
9 58 
8 38 
1516 
12 41.9 
Water, - 
15 
1,000 
58 5 40 
22 3640 
3 12.4 
810.6 
9 57.5 
8 30.5 
15*15.6 
12 46.2 
Kali dissol- 
ved in water, 
9 
416 
58 ' 5 40 
27 45 56 
4 2 
10 26 
12 54 
11 12 
20 36 
17 24 
Oil of Tur- 
pentine, 
84 
0.885 
58 5 40 
33 2012 
4 56 
13 52 
18 46.1 
16 14 
31 8 
27 28 
Flint glass. 
No. 3. 
3.512 
27 41 35 
173516.6 
3 8 
8 22 
10 46 
9 50 
19 10 
1710 
Flint glass, 
No, 30. 
3.695 
21 42 15 
14 3 9 
2 35.6 
6 56.8 
9 12.6 
8 19 
16 15.6 
14 32.2 
Crown glass. 
No. 13. 
2.535 
43 27 36 
25 26 35.4 
3 5 
8 14.4 
10 28.2 
9 10 
1714.8 
14 48.4 
Crown glass, 
1 M. 
2.756 
42 56 40 
26 39 13 
3 32.8 
9 37.6 
12 29.8 
11 1.6 
20 53.6 
18 17.4 
Flint glass, 
No. 23, 
3,724 
6015 42 
49 55 13.2 
11 12.6 
31 14.8 
41 21.4 
38 14.8 
114 45.2 
1 8 3.6 
Flint glass, 
No. 23. 
3.724 
45 23 14 
32 4512.2 
6 26 
17 47.8 
23 31.8 
21 23.8 
41 33.4 
37 28.8 
In order to measure these angles, I employed the same theo- 
dolite which I have already mentioned. The measures were ta- 
ken six times. The distance of the theodolite from the window 
of the dark room into which the light entered, was only S4 feet. 
The correction of the angle ^ arising from the distance 4.25 
inches of the prism from the axis of the theodolite, would have 
been very considerable. In order to avoid the uncertainty 
which arises from a great correction, I determined the angle 
for the light of a lamp, as the rays D, Fig. 5. and R, Fig. 4. 
Plate VII. Vol. IX., have the same refrangibility. In this case 
the lamp was at a distance of 692 feet ; the correction of (a was 
