312 Prof. W. D. Harkins on the 



quantitative analyses have been made, which falls upon the 

 earth's surface from space. The bodies which fall are called 

 meteorites, and no matter what theory of their origin is 

 adopted, it is evident that this material comes from much 

 more widely distributed sources, so far as its immediate 

 origin is concerned, than the rocks on the surface of the 

 earth. In any event, it seems probable that the meteorites 

 represent more accurately the average composition of 

 material at the stage of evolution corresponding to the earth, 

 than does the very limited part of the earth's material to 

 which we have access. 



That the abundance of the elements in the meteorites is 

 determined more largely by the factors concerned in the 

 building of nuclei than by those of a chemical or physical 

 nature, may be illustrated by citing a fact concerning the 

 development of the theory. Before the writer had made 

 any study, or had any sufficiently specific knowlege, of the 

 composition of the meteorites, he was able to predict the 

 general abundance relations which would exist, by using as 

 a basis the hydrogen-helium theory of nuclear structure 

 which he had previously developed. Extensive evidence in 

 support of this idea has already been published in an earlier 

 paper and should be consulted there *. 



The above considerations indicate that the composition of 

 meteorites should be more intimately related to nuclear 

 stability than the composition of the earth's crust. Never- 

 theless it will be found that so far as the general relations 

 are concerned there is excellent agreement between the two. 



The High Relative Frequency -of Occurrence of Even 

 Numbers of Electrons and Protons in Nuclei. 



The numerical relations of the electrons in atom nuclei 

 should be of interest to those engaged in the study of the 

 theory of numbers, since even numbers occur much more 

 frequently than odd numbers. It has been found that 

 350 stone meteorites fall upon the earth's surface during 

 the time in which 10 iron meteorites fall. Quantitative 

 analyses are available for about 320 iron and 150 stone 

 meteorites. If these are calculated to the ratio given above, 

 and expressed in atomic percentages, it is found that the 

 five most abundant elements are oxygen (53*16 per cent.), 

 silicon (15*35 per cent.), magnesium (13*15 per cent.), iron 

 (12-79 per cent.), and sulphur (1*46 per cent.), all of these 

 being elements of even atomic number. Thus these five 

 * J. Am. Cliem. Soc. xxxix. pp. 856-879 (1917). 



