Resonance Spectra of Sodium Vapour. 
597 
line are doublets, though they are so faint as to be only just 
discernible on the photographs obtained thus far. 
The wave-lengths in the blue and 
in the following table. 
missing* 
region are given 
Two lines in the series appear to be 
5007 * Differences. 
5004 
4995 3 6 
4990 
4962 
4935* 
4927 35-5 
4867 
4804 * 
4860 3o '° 
4828-5* 
4823-7 6o '° 
4793* 
4790-5 3o '° 
4757'5 * 
4756-5 
4727 34 '° 
4723* 
4720 3S 
4690* 32-5 
4657 "5* 325 
4625 * 
The lines in the yellow-green region are given below. 
The intensities are designated roughly by numerals, 1 meaning- 
very faint. 
5534-4 
1 
5447-1 
2 
5391-9 
55303 
1 
5445 9 
2 
5391-1 
2 
5509 
1 
5442-1 
2 
5388-3 
1 
5504 
3 
5440-9 
5 
5387-1 
1 
5500-9 
6 
5438-3 
1 
5379-1 
4 
5499-5 
1 
5436-7 
1 
5377-7 
4 
5491-6 
2 
5431-1 
5376-2 
1 
5490-1 
2 
54295 
53740 
5 
5488-7 
5 
5426-8 
5373-5 
7 
5474-5 
5 
5425-4 
5372-5 
1 
54735 
6 
54239 
5358 
2 
5470-5 
2 
5413-2 
8 
5357-3 
2 
54690 
2 
5411-9 
8 
5355-7 
1 
5463-8 
1 
5410-4 
2 
5336-8 
6 
5462-3 
1 
5408-3 
5 
5335-6 
2 
5459-4 
7 
5407-5 
5 
5334-1 
1 
5458-0 
3 
5394-8 
2 
5299-8 
2 
5456 "5 
5 
5392-8 
Silver Excitation. 
In the earlier work it was believed that the silver line 
5209 excited the same series as the cadmium line 4800. 
This is now known to be an error due to the insufficient 
Phil. Mag. Ser. 6. Vol. 15. No. 89. May 1908. 2 8 
