li THE ROYAL SOCIETY OF CANADA 



McLennan and Thomson.^ The arsenic metal was placed in the steel 

 annulus which was heated by a Bunsen burner ; the vapour being 

 driven into a gently burning flame. 



Spectrograms were taken with a Hilger type A quartz spectro- 

 graph on Schumann plates prepared by the Adam Hilger Co. The 

 exposures were of about seven hours' duration and the following 

 arsenic radiation was recorded in addition to the ordinary Bunsen 

 flame spectrum. 



Lines at A 3266 A.U., A 2860 A.U., X 2780 A.U., A 2350 A.U. and 

 A 2288 A.U. and bands with heads at A 2634 A.U., A = 2570 A.U., 

 A = 2503 -5 A.U. and A 2437-3 A.U., the weaker parts of the bands 

 being towards the ultra violet. 



A number of these correspond to flame lines found by Eder and 

 Valenta.^ 



VII L Summary 



(a) Thallium 



1. In addition to absorptions of thallium already discovered 

 by Guthrie', further absorptions were obtained as arc reversals. 



2. These additional absorptions in the ultra violet region were 

 confined to the two series y= (2,p2) — (m,d') for values of m = 6— 14 

 inclusive and v= (2,p2) — (m,s) for m = 5-5 — 11-5 inclusive. 



3. The series v= (2,p2) — (m,s) has been observed for values of 

 m = 10 • 5 and m = 1 1 • 5 for the first time. 



4. No absorption was obtained in the region 1700 A.U. with the 

 thallium arc in vacuo. 



(b) Alnminium 



1. The absorption spectrum of aluminium has been found to 

 consist of fourteen bands in the extreme ultra violet. 



2. As with thallium these absorptions are given by the series 

 y = (2,p2) — (m,d') for values of m = 6— 14 inclusive and v = (2,p2) 

 — (m,s) for values ofm = 4-5 — 8-5 inclusive. 



3. The series y = (2,p2) — (m,d') has been verified for m=12, 13 

 and 14 and the series v= (2,p2) — (m,s) for m = 6-5 and 7-5 for the first 

 time. 



(c) Lead 



1. In all, 19 absorption bands of lead were measured. 



1 McLennan and Thomson. Proc. Roy. Soc. A. Vol. 92, 1916, p. 584. 

 ^ Eder and Valenta, Atlas, Typischer Spektren. 

 ' Guthrie — loc. cit. 



