[mclennan-zumsteinI 



SPECTRA OF LEAD 



15 



X X + / X + 2 X+J X + 4 



DIFFUSE 5Ef?)ES 



Figure 4 



the principal series they show that the wavelengths selected are 

 fairly well represented by a Ritz-Rydberg formula. All the wave- 

 lengths given in Tables III and IV correspond very closely to wave- 

 lengths found in the emission spectrum of lead and most of them 

 showed reversal in the experiments made by McLennan, Young, and 

 Ire ton. 



In the series which have been given above no provision is made 

 for the wavelength A = 2833 -17. This line it will be noted was strongly 

 absorbed by non-luminous lead vapour, and it consequently should 

 appear in some series which possesses fundamental characteristics. 



Having in mind the series spectra of mercury, zinc and cadmium 

 it was thought that possibly on later investigation the wavelength 

 A =10500 A*U might turn out to be the first member of a series n = 

 (2-5, S) — (m,P) instead of being the first member of the series n = 

 (1 -5, S) — (m, P). In this case one would naturally turn to the view 



