82 
PROFESSOR W. N. HARTLEY AND MR. W. E. ADENEY 
When the corrections in the preceding tables are seen to vary slightly it is owing 
to small errors which are introduced by the re-adjustment of the grating. The 
corrections applicable to each spectrum are found by converting the values obtained 
for the cadmium lines given by the fixed electrode into the wave-lengths given above. 
In the following tables the wave-lengths of a number of lines are compared with 
measurements of previous observers. That these numbers agree in a very satisfactory 
manner gives us some confidence in our method of working and in the probable 
accuracy of the wave-lengths we have adopted for the cadmium lines, as derived from 
our several measurements. With the exception of the lines 3402'9, 2196’4, and the 
triple group 3260 , 2, 3251’8, 3249‘5, our numbers agree well with those of M. Corntj, 
but at these points the difference is considerable. We have carefully measured these 
lines directly and we are inclined to consider our numbers correct. M. Cornu did 
not directly measure these lines, but derived the numbers he has given from a 
comparison of his photographs with his map of the solar spectrum. But the reason 
why the wave-lengths we have given are probably the more correct lies in the fact 
that about this region there are many iron lines, and our measurements of iron agree 
with those of M. Cornu, while, if our cadmium lines departed from accuracy as far as 
they differ from those of M. Cornu, this difference would occur in the iron lines. 
Comparison of the wave-lengths of lines from the spectrum of cadmium. 
Mascart. 
Cornu. 
Hartley 
and Adenet. 
Lecocq. 
Thalen. 
7 
4414-5 
4414-6 
4414 
8 
3985-6 
3994-5 
# , 
3995 
9 
3607-5 
3609 
3609-6 
10 
3464-5 
3465-5 
3465-4 
11 
3403-0 
3401-5 
3402-9 
12« 
3260-2 
„/3 
. . 
. . 
3251-8 
» 7 
3287-5 
3247-0 
3249-5 
17 
2763-4 
2747-7 
2747-7 
18 
2574-2 
2572-3 
2572-2 
23 
2318-2 
2313-5 
2313-6 
24 
2265-6 
2265-5 
2265-9 
25 
2217-6 
2194-5 
2196-4 
No. 8 is an air line. 
Nos. 9 and 10 we discovered to be doublets, but the numbers here given are those 
assigned to the more refrangible lines of each. 
No. 12 is a triple group ; this fact was recognised by M. Cornu. The wave-lengths 
of two iron lines close to this group are the following:— 
Cornu. Hartley and Adenet. 
3246-2 3246-3 
3242-7 3243 0 
