Constitution and Stability of Atom Nuclei. 307 



The atomic weight, or what is now seen to be the element 

 weight, has been determined by a combination of chemical 

 with vapour density or other methods. The element weights 

 thus obtained gave evidence in themselves that part of the 

 elements are mixtures, and part are pure or nearly pure 

 atomic species, and in the latter event, the chemical method 

 gives the actu.il atomic weight, which may be determined 

 also by the positive ray method. The atomic weight of the 

 pure species, determined by either of these two methods, 

 will be designated by P, and N will be defined as equal to 

 P — M. Since N is simply the difference of two experi- 

 mentally determined numbers, it, itself, is experimental. 



Very extensive data related to the abundance of the 

 elements in the earth's crust have been collected by Clarke, 

 by Vogt, and by Washington, while similar data for the 

 meteorites have been gathered together by Farrington and 

 by Merrill. It has been shown by the writer that the 

 characteristics of the meteorites are such as to indicate that 

 the relative abundance of the elements which they contain 

 has been affected less by segregation than is the case for the 

 surface of the earth. The data concerning the latter are 

 made less significant by the fact that the samples which 

 have been analysed seem to represent only an extremely 

 thin surface layer, while the meteorites represent a much 

 greater distribution in space. 



The outline given below presents a list of seven experi- 

 mental correlations, stated first in experimental language, 

 and second in the language of hypothesis. In this outline : 



Experimental Meaning. Hypothetical Meaning. 



P = Atomic weight. Number of Hydrogen Nuclei or 



Protons *. 

 M= Atomic or Moseley Number. Net positive charge on Nucleus. 

 N = P — M. Number of negative electrons in 



nucleus. 

 A = Abundance (Atomic percentage). Related to atomic stability. 



1 (a). Atoms in which N is even are many times more 

 abundant than when N is odd ; about 33 times as 

 abundant in the meteorites, and about 40 times as 

 abundant on the earth's crust. 

 (b). Nuclei, or groups of electrons and protons in nuclei, 

 which contain an odd number, are in general much less 

 stable than those which contain an even number of 

 negative electrons. 



* So far as the writer can learn, the word proton was suggested by 

 Rutherford for use in designating the hydrogen nucleus. This will also 

 be designated as the positive electron in the present paper. 



Y2 



