THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES 



OCTOBER 1917 



XXVI. On the Origin of the Line Spectrum emitted by Iron 

 Vapour in the Explosion Region of the Air-Coal Gas 

 Flame. By G. A. Hemsalech, Honorary Research Fellow 

 in the University of Manchester *. 



[Plates II. & III.] 

 § 1. Introduction. 



IT has been shown f that there are two different types of 

 iron cone lines : firstly, those forming Class II., which 

 appear likewise, though only feebly in the mantle, but grow 

 more intense on passing to flames of higher temperature ; 

 and, secondly, Class III. lines, which are observed solely in 

 the cone. The special interest attached to Class III. lines 

 is that among them are found a number of lines which had 

 always been regarded as due to the more violent modes 

 of excitation, such as prevail in the arc or spark. Thus 

 Mons. de Watteville and myself \ were able to identify 

 in the supplementary spectrum a considerable number of 

 Duflield's polar A and polar S lines § ; further, we recog- 

 nized three of Lockyer's enhanced lines, namely, XX 3864, 

 3872, and 3936. With regard to the last-named line, which 



* Communicated by Sir E. Rutherford, F.R.S. 

 t Hemsalech, Phil. Mag. ser. 6, vol. xxxiii. p. 1 (1917). 

 X Hemsalech and de Watteville, Comptes JRendus de VAcademie des 

 Sciences, vol. cxlvi. p. 1389 (1908). 



§ G. W. Duffield, ' Astrophysical Journal/ vol. xxvii. p. 260 (1908). 



Phil. Mag. S. 6. Vol. 34. No. 202. Oct. 1917. R 



