EJEV. T. E. EOBINSON ON SPECTEA OF ELECTEIC LIGHT. 
961 
Some of these are peculiar. In air, C.P., No. 12 is the brightest of all, ^ is very 
brilliant, so is No. 46. The H, C.P., is also greatly developed. It was taken at the 
negative electrode only. Nos. 2, 29, and 48 reach quite across the spectrum ; the others 
more or less, but on an average about one-third of the way from each electrode, being 
brightest at the negative. The deposit in the tubes was very considerable, but it does 
not seem to have cut off much of the spectra. To examine the effect of the diameter of 
tube, I took (with Duboscq) the air P. in a compound tube, of which the wider parts 
were 0'4 inch bore, and the narrower 0-04 and 1‘5 long. The distance between the elec- 
trodes was 5 inches. The discharge was pretty bright in the narrow parts, and red, 
except on the negative wire, where it was blue. They are as follows ; — 
Narrow. 
Blue negative. 
Bed positive. 
1. 
32 a 
38-1 f. 
2. 
49*1 vf. 
3. 
32 
58 
58 vf. 
58 vf. 
many 
r 
4. 
33 
0-6 
J vf. 
5. 
5-3 I 
n. 
6 f. 
6. 
7-3 J 
7 vf. 
7. 
e 
9-4 
ff. 
8. 
11 b. 
10-7 c. 
10*5 nb. 
others. 
9. 
14 ' 
some. 
10. 
K 
16-4 J 
f. 
11. 
20 t 
20*71 c. 
12. 
22*4 
w. 
23*4 1 c. 
eo 
13. 
25*7 
W. 
25*7 J c. 
14. 
28*4 nf. 
29*4 f. 
one. 
15. 
.31-4 nf. 
32*1 nc. 
30*8 vf. 
16. 
34.4 C- 
35*1 vf. 
17. 
37*5 c. 
37*8 f. 
37*8 nf. 
18. 
40-8 nb. 
40*8 nc. 
19. 
44-1 w. 
44*1 vf. 
44*1 f. 
20. 
46*7 vf. 
21. 
50 b. 
51*3 c. 
49*3 vf. 
22. 
33 
55*3 b. 
54*7 f. 
54*3 f. 
23. 
34 
0*4 b. 
0*1 f. 
0*4 f. 
24. 
7-3 b. 
6*9 f. 
6*9 f. 
25. 
13-4 nb. 
12*7 vf. 
13*4 vf. 
26 . 
18 ] 
c. 
27. 
18*6 f. 
18*6 w. 
28. 
19-3 
c. 
29. 
26-5 b. 
25*8 c. 
26*5 vf. 
30. 
33-1 c. 
33*4 vf. 
31. 
39-6 c. 
32. 
49-5 vf. 
33. 
57-8 vf. 
The three evidently represent the same system of lines, for those missing in the 
second and third have been lost by their faintness. Nos. 12, 19 and 46, Table IX., are 
resolved by Duboscq into pairs. It also shows 17 which were not visible in the other. 
Nos. 5 and 11 of that again are not found in these: the first of these is almost peculiar 
to R. spectra ; and its not being visible in the narrow tube here seems to argue that 
condensed discharge cannot show it. 
