Constitution and Stability of Atom Nuclei. 319 



Thus fig. 4 (PL XII.) shows clearly that each element of 



EVEN ATOMIC NUMBER IN" EVERY CASE IS MUCH MORE ABUN- 

 DANT THAN THE TWO ADJACENT ODD NUMBERED ELEMENTS *. 



It seems obvious that the rare gases, helium, neon, and 

 argon, would not be held by the gravitational attraction of 

 such a small body as a meteorite, so the data for these 

 elements have not been included in the plot; since the 

 studies outlined here relate to the general abundance 

 relations of the elements and atomic species as conditioned 

 by atomic stability. The absence of these substances from 

 the meteorites, except for the small amounts due to their 

 solubility or to inclusion, would be the result 6*f their 

 physical properties even if the body from which the meteorites 

 were originally derived contained considerable percentages 

 of these elements. 



* The alternation of the abundance of the elements between even and 

 odd atomic numbers cannot well be shown for the heavy elements in the 

 meteorites, since they occur in such small percentages, and on the surface 

 of the earth the segregative effects of the chemical and physical 

 properties have undoubtedly obscured the contrast between odd and even 

 except where it is so extremely prominent as it is among the light atoms. 

 The rare earths, however, as the writer had learned by experience, are 

 extremely difficult to separate, so it seemed that in so far they are 

 segregated from other elements, this need not destroy altogether the 

 relations due to atomic stability. In order to get as reliable an estimate 

 as possible, two noted workers were consulted in the year 1916. These 

 were C. James and 0. W. Balke. Neither of these was given any hint 

 of the writer's theory that the even numbered elements should be the 

 more abundant. The remarkable feature was that there was agreement 

 in the two estimates and a third made by the writer in every individual 

 instance. 



Abundance of the Rare Earths, showing the Relatively greater 

 Abundance of the Elements of Even Atomic Number. 



Atomic 







! Atomic 







Number. 



Abundance 



Element. 



Number 



, Abundance. 



Element. 



55 



c 



Caesium. 



64 



r 



Gadolinium. 



56 



ccc 



Barium. 



65 



rrr 



Terbium. 



57 



c 



Lanthanum. 



66 



r 



Dysprosium 



58 



cc 



Cerium. 



67 



rrr 



Holmium. 



59 



r 



Praseodymium. 



68 



r 



Erbium. 



60 



c 



Neodymium. 



69 



rrr 



Thulium. 



61 



rrr 



Unknown. 



70 



r 



Ytterbium. 



62 



c 



Samarium. 



71 



rrrr 



Lutecium. 



63 



rr 



Europium. 









In the Table c represents relatively common, and r relatively rare. 

 while a repetition of the letter serves to emphasize the commonness or 

 rarity. The estimates are intended only to contrast adjacent elements, 

 and not to show the relative abundance of widely separated ones in the 

 Table. It is seen that in each case the estimates indicate the greater 

 abundance of the elements of even atomic number. 



