THE ULTRA-VIOLET SPECTRA OE TUL ELEMENTS. 
219 
Gold. 
Gold also gives ns but few lines. The three lines we record are perhaps harmonically 
related. 
Gold lines. 
Approximate 
wave-length. 
Remarks. 
3122-8 
2675-4 
Reversed. 
2427-5 
Ditto. 
Thallium. 
Groups of thallium lines manifestly similar to one another recur, and are probably 
harmonically related. This recurrence is more evident in the photographs in which the 
lines which are expanded and reversed by the introduction of fresh metal are at once 
recognised. The pairs at 2921, 2710, 2609, and the lines at 2552, 2517 seem to 
fall into one series. 
Thallium lines. 
Approximate 
wave-length. 
Remarks. 
Approximate 
wave-length. 
Remarks. 
3775-6 
2714-6 
Very diffuse. 
3528-3 
2710-4 
1 Reversed. 
3517-8 
2708-8 
/ Strong, diffuse reversed. 
3228-1 
2699-7 
Very diffuse. 
2943-9 
2665-0 
Diffuse. 
2921-3 
1 
2652-3 
2917-8 
/ Very strong. 
2609-4 
1 Reversed. 
2895-2 
2608-6 
/ Strong, reversed. 
2825-8 
2552-0 
Reversed. 
2826-9 
2517-0 
Diffuse. 
Aluminium. 
The spectrum of aluminium is comparatively simple. The well-known pair of lines 
between H and K seem to be repeated twice in the region above without much, if any, 
diminution of strength, but we have not observed any such lengthened sequence of 
repetitions of these lines as we have of the lines of magnesium and other metals. 
Higher on the scale we come to another series of groups which are triplets, or perhaps 
quadruple groups, for the first and strongest group shows a faint fourth line which we 
have not observed in the succeeding groups. The repetitions we record are only two, 
2 f 2 
