﻿Principal Series in Spectra of the Alkali Metals. lid 



inversely as the fourth power of the distance, seems to show 

 that the atom of iron must come under one of the special 

 cases above mentioned, having a centre ring with only one 

 or two electrons. The force in this case may be inversely 

 as the square of the distance. This is shown by the equations 

 for the hydrogen atom, (48) and (49) above, where the first 

 term due to the magnetic force contains the inverse second 

 power of the distance, showing that for hydrogen atoms 

 at a great distance, having parallel axes, the attraction is 

 inversely as the square of the distance. This suggests that 

 possibly the rings of electrons in fig. 3 * of the former 

 paper are correct, for there iron and cobalt have a single 

 central electron, and nickel two central electrons, which will 

 give rise to the same law of variation of the force with the 

 distance as that in hydrogen. 



In this paper the positive charge in each atom is supposed 

 to be at rest free from vibration of its whole mass, and long- 

 waves of radiant heat are attributed to the vibration of this 

 mass. The period of this vibration in the hydrogen molecule 

 was given in the former paper. It should be considered, 

 therefore, that the work in this paper applies to the state of 

 matter at the absolute zero of temperature. 



LXXXI. On the Principal Series in the Spectra of the 

 Alkali Metals. By W. Marshall Watts, U.Sc.\ 



IN the Philosophical Magazine for 1908 (xvi. p. 945) 

 Wood describes the absorption spectrum of sodium 

 vapour in which he measured 48 lines of the principal 

 series forming the most extended " Balmer series " hitherto 

 observed. 



Bevan J applied Wood's method to the other alkali 

 metals, and observed extended series in lithium, potassium, 

 rubidium, and csesium. He also discusses the representation 

 of these long series by formula, obtaining very close results 

 by the use of the formula employed by Mogendorff in 1906 

 and by Hicks in 1910, viz., 



109675 



O.F. = C.F. 



(W/x+£)\ 



* Loc. cit. 



t Communicated by the Author. 



| Proc. Koy. Soc. lxxxiii. p. 4:23 (1910), lxxxiv. p. 209, lxxxv. 

 pp. 54, 55, lxxxvi. p. 300 (1911). 



