Vol.. 7, 1921 PHYSICS: R. A. MILLIKA N 293 
10 
9 
7 
6 
5 
4 
3 
2 
1 
5 10 15 20 25 30 35 40 
Atomic Number 
L a lines of Li, Be, B, C, N, O, F, Ne, Na, Mg and Al 
A glance at the figure shows that we now have the complete outline of all of 
the types of radiations which are emitted by atoms of small atomic number. 
It remains only to fill in the details of their K a and L a spectra. One 
interesting fact which appears from a glance at the whole series of spectra 
of elements from hydrogen to neon is that atoms of odd ordinal all appear 
to have simple, few-lined spectra, while those of even ordinal number 
have much more complex spectra. 
1 Physic. Rev., 10,1917 (205). 
*Astroph. J. 52, 1920 (47). 
