1915-1916.] Explanation of the Satellites of Spectral Lines. 203 
oscillation of one definite frequency is worthy of consideration as a means 
of explaining the complexity of spectra. The old idea, according to which 
we bad a number of particles moving under a system of attractions accord- 
ing to the laws of dynamics, and which in view of the complexity of the 
subject usually relapsed into generalised co-ordinates, has not proved 
successful ; and the modern view, which puts electrons into the molecule, 
as if they were stones into a bag, assigning a definite electron to each 
line, does not seem very promising either. So there is room for fresh 
hypotheses. 
( Issued separately November 29 , 1916 .) 
