ON THE MEASUREMENTS OP WAVE-LENGTHS. 
91 
The Spectrum of Air. 
Scale- 
numbers. 
Description of lines. 
Eloctrodes employed. 
Remarks. 
Copper. 
Aluminium. 
Mean. 
Wave- 
Wave- 
Wave- 
lengths. 
lengths. 
lengths. 
7-97 
Faint. 
4674-2 
. . 
4674"2 
The air lines being diffi- 
8-60 
Faint. 
4660-2 
. , 
4660-2 
cult to measure, we 
9-08 
/Weak. 
4647-2 
4647-2 
have taken the mean 
9-48 
/ Weak. 
4641-2 
4641-2* 
wave - lengths derived 
10-00 
Strong . 
4629-0 
4628-7 
4628-9 
from two or three 
10-40 
W eak. 
4619-9 
* • * 
4619-9 
different photographs. 
10-74 
Weak. 
4612-3 
4612-3 
*Thal^n gives this line as 
11-10 
Weak. 
4605-6 
4605-6 
double. 
11-40 
Weak. 
4600-1 
. . 
4600-1 
11-85 
W eak. 
4595-0 
4595-0 
11-89 
W eak. 
4589-3 
4589-3 
13-80 
Faint nebulous band 
4553-2 
4553-2 
Faint. 
4543-4 
4543-4 
14-97 
f Weak band. 
4530-1 
4530-1 
15-25 
\ Faint, nebulous .... 
4523-0 
4523-0 
15-7 
Weak, fine. 
4513-7 
4513-7 
15-9 
Weak. 
4506-6 
4506-6 
16-96 
Weak, fine. 
4476-6 
, . 
4476"6 
17-48 
Weak band. 
, 4466-1 
. . 
4466-1 
18-23 
Weak, fine. 
4458-7 
4458-7 
19-25 
Strong. 
4446-3 
4445-8 
4446-0 
20-03 
/ Weak nebulous band . . 
4433-0 
4432-2 
4432-6 
20-30 
\ Weak, nebulous .... 
4426-3 
4425-5 
4425-9 
20- 89 
21- 01 
j Weak. 
\ Weak. 
4415-5 
4413-6 
| From the platinum plate. 
21-80 
Faint. 
4403-11 
4402-0 
4402-6 
21-93 
W eak. 
4395-0 
4394-8 
4394-9 
22-5 
Very faint. 
. . 
4386-3 
4386-3 
22-83 
Faint. 
4378-1 
4377-9 
4378-0 
23-61 
Weak. 
4365-9 
4365-7 
4365-8 
24-16 
Very faint, nebulous. 
4356-4 
4356-4 
24-53 
/Weak, fine. 
4350-7 
4350-2 
4350-5 
24-67 
< Strong. 
4348-4 
4348-0 
4348-2 
24-83 
/Weak, fine. 
4343-8 
4344-0 
4343-9 
25-32 
Faint. 
4336-0 
4335-8 
4335-9 
25-63 
Faint. 
4330-9 
4330-6 
4330-8 
25-78 
/ Faint. 
4327-2 
4326-6 
4326-9 
25-88 
\ Faint. 
4324 6 
4324-6 
4324-6 
26-31 
/ Weak. 
4319-0 
4318-5 
4318-7 
26-44 
1 Weak. 
4316-3 
4316-1 
4316-2 
2715 
/ Very faint, nebulous . . 
4306-1 
4306-9 
4306-5 
\ Very faint. 
. . 
4302-0 
4302-0 
27-16 
Faint, nebulous ... 
42903 
4289-7 
4290-0 
28-93 
/ Faint, nebulous .... 
4275-3 
4275-3 
\ Very faint, sharp .... 
. . 
4274-3 
4274-3 
29-49 
Very faint ...... 
4265-8 
4264-9 
4265 "4 
30-21 
Faint. 
4253-4 
4253-3 
4253-4 
30-95 
f Strong, nebulous .... 
4240-2 
4241-0 
4240 6 
31-21 
< Strong, nebulous .... 
4236-7 
4236-0 
4236-4 
31-68 
[ Fairly strong, nebulous . 
4229-1 
4228-7 
4228-9 
31-98 
Faint, nebulous .... 
4222-3 
4222-8 
4222-6 
32-38 
Faint. 
4217-1 
4215-9 
4216-5 
