370 
MR. E. G. BILHAM ON THE SPARK SPECTRUM OF 
Table V. 
Wave-length. 
Intensity. 
Class. 
Wavedength. 
i 
Intensity. 
I 
Class. 
" 
3467-63 
2 
II. 
5035-55 
7 
rvi.i 
3469-61 
2 
II. 
5080-70 
5 
. tv 
3471-50 E. 
2 
IV. 
5081-30 
5 
j 
> IV. 
4067-20 E. 
6 
IV. 
5099•50 
3 
L v 
4520-16 
2 
III. 
5100-13 
3 
v - 
4547-16 
2 
V. 
5115-55 
6 
V. 
4600-58 
3 
IV. 
5137-23 
4 
III. 
4605•20 
6 
V. 
5142-96 
9 
- j 
IV. 
4648-89 
8 
V. 
5146-64 
4 
IV. 
4667-95 
6 
V. 
5155-92 
4 
IV. 
4686-41 
4 
III. 
5168-83 
4 
IV. 
4714-59 
10 
V. 
5265-89 
1 
V. 
4732-00 
3 
1 v 
5268-59 
2 
V. 
4732-66 
3 
J 
5371-64 
4 
V. 
4752-58 
3 
[VI.]* 
5411-50 
2 
IV. 
4756-70 
8 
V. 
5424-85 
4 
III. 
4764-07 
5 
V. 
5436-10 
2 
III. 
4786-66 
9 
V. 
5477-13 
10 
II. 
4807-17 
6 
V. 
5510-28 
3 
[VI.] 1 
4829-18 
3 
] 
5578-98 
2 
III. 
4831-30 
3 
[ V. 
5588-12 
2 
III. 
4832-86 
1 
J 
5592-44 
4 
V. 
4855-57 
6 
IV. 
5615-00 
3 
V. 
4866-42 
6 
V. 
5709-80 
3 
III. 
4873-60 
6 
V. 
5712-10 
2 
III. 
4887-16 
2 
V. 
5715-31 
5 
V. 
4904-56 
6 
IV. 
5748-57 
1 
III. 
4918-53 
6 
V. 
5754-86 
4 
III. 
4936-02 
4 
V. 
5761-10 
3 
V. 
4953-34 
4 
V. 
5805•45 
9 
jj 
IV. 
4980-36 
6 
IV. 
5858-03 
3 
IV. 
4984-30 
6 
IV. 
5893-13 
3 
III. 
5017*75 
6 
V. 
6116-34 
4 
1 
III. 
* Shaded to violet. 
12. Summary. 
1. The nickel spark spectrum has been investigated under pressures up to eleven 
atmospheres. 
2. The lines exhibit a remarkable variety of behaviour and may be divided into 
five classes, according to their types of reversal or broadening. 
3. With increase of pressure the enhanced lines decrease in intensity and broaden 
symmetrically. 
4. Gas lines disappear under pressure. 
5. The general effect of pressure on the relative intensities of the lines is similar 
to that of including self-induction in a spark circuit. 
6. All lines are displaced towards the red end of the spectrum. 
7. The average shifts are the same for symmetrical and unsymmetrical reversals. 
