MR. J. E. H. GORDON ON MEASUREMENTS OF ELECTRICAL CONSTANTS. 443 
Refractive index of light flint glass. 
Specific gravity 
V / K = l-7342 
3d 9 8 Gordon. 
3'20609 Hopkinson. 
Ray. 
Wave length. 
A 
Ray. 
Wave length. 
Gordon. 
Hopkinson. 
Bright line in extreme red . 
D. 
h . 
\ . 
Bright line in central blue . . 
Band in extreme violet . 
5-892 
j 5-174 | 
1-5685 
1-5722 
1-5787 
1-5805 
1-5879 
1-5920 
1-5685 
1-5740 
j 1-5803 
J 1-5839 
/ 1-5928 
{ 1-6007 
B 
D 
b 
F 
G 
6-867 
3-968 
Which give p A=05 = 
f 1’547 Gordon from D and b. 
L1 *555 Hopkinson from B and H x . 
Refractive index of hard crown glass. 
Specific gravity 
2 - 484 Gordon. 
2’48664 Hopkinson. 
V /K = l*7629. 
Ray. 
Wave length. 
M- 
Ray. 
Wave length. 
Gordon. 
Hopkinson. 
Bright line in extreme red . 
1-5022 
1-5141 
B 
6-867 
D. 
5-892 
1-5045 
1-5176 
D 
h . 
h . 
j 5-174 | 
1-5083 
1-5093 
J 1-5215 
b 
Bright line in central blue . 
1-5017 
1-5236 
F 
Band in extreme violet . 
1-5132 
/ 1-5288 
f 1-5333 
G 
Hi 
3-968 
-rrji • r • f 1 - 491 Gordon from D and b. 
Which give p A=Q0 = 4 
L 1‘504 Hopkinson from B and H x . 
I here give for what it may be worth an attempt to determine for two glasses for 
what wave length of light p would equal \/K. 
To determine the wave length of the ray for which p= v /K, we have 
"= A +! 
3 L 2 
