DR. T. R. MERTON AND PROF. J. W. NICHOLSON ON 
1 (W) 
It does not appear to be necessary to add any further details of the experimental 
ari'ano'ements in these cases, which have been dealt with in an earlier section in 
general terms. 
The magnification of all the enlargements in these cases was the same, the interval 
Ijetween AA6678, 3888, being 147 mm. as against 44'95 mm. on the original plate. 
Tlie magnification is therefore 
ui = 147/44-95 = 3-270. 
The following notation will be adopted for brevity :— 
(rt) = Spectrum of pure Helium at very low pressure, the resistance of the tube 
corresponding to about 2 cm. alternative spark gap. 
(5) = “(Ordinary” spectrum of pure Helium from the capillary with 1 mm. dark 
space. 
(c) = Spectrum of Helium containing a trace of Hydrogen, just sufficient to show 
the Hydrogen lines. Taken from the capillary (l mm. dark space). 
((7) = Spectrum as in (c), but with a larger admixture of Hydrogen. 
Table XII. gives the observed heights of the various lines ;—■ 
Table XII.—Observations of Helium under Various Conditions. 
A. 
d . 
A 
Photograph («). 
Photograph (l>). 
Photograph (r). 
Photograph (7). 
h. 
h. 
h. 
« 
h. 
70(15 
0 • 333 
absent 
10-6 
10-0 
11-3 
66 7 s 
0 • 339 
5 - 3 
18-0 
17-9 
16-8 
5 S 76 
0 • 396 
9-0 
31-8 
30 - 3 
19-0 
5047 
0-414 
al».seiit 
8-3 
7-7 
10-3 
5015 
0-415 
9-4 
16-6 
14-8 
15-8 
v.yi-1 
0 - 41.5 
5-0 
13-8 
13-0 
13-3 
471 .-! 
0-430 
6 - 3 
15-5 
14-4 
16-6 
4471 
0 - 453 
11-5 
19-9 
18-1 
18-7 
4437 
0-461 
absent 
6 - 7 
5-9 
7-6 
43 SS 
0-475 
4-3 
10-1 
9-3 
10-0 
4160 
0 - 556 
absent 
1-3 
al)sent 
3-0 
4144 
0 - 569 
absent 
4-9 
3-7 
5-0 
4131 
0-583 
absent 
7-7 
6-6 
7-9 
4036 
0 - 650 
4-0 
9-3 
8-4 
9-4 
4009 
0-664 
, absent 
0-9 
absent 
1-5 
3965 
0-707 
.) . .) 
6-6 
5 • 3 
6-4 
388 s 
0-815 
3-6 
11-1 
10 - 1 
10-1 
The next table (Table XIII.) gives tbe corresponding photographic intensities of 
the lines, as the results of calculation by the usual formula. 
