446 



SCIENCE 



[N. S. Vol. XL VI. No. 1193 



those below give the percentages of the 

 elements. It will be noted that the even- 

 numbered demerits are in every case more 

 abundant than the adjacent odd-numhered 

 elements. The helium group elements form 

 no chemical compounds, and are all gases, 

 so they could not be expected to remain in 

 large quantities in meteorites. For this 

 reason, and also because the data are not 

 available, the helium or zero group is 

 omitted from the table. 



Prom this table it will be seen that while 

 high percentages, as great as 72 per cent, 

 in one case, are common among the even- 

 numbered elements, the highest percentage 

 for any odd-numbered element is less than 

 one per cent. (0.39 for aluminium). 



If we now turn to the composition of the 

 earth, it is found that the atoms of even 

 atomic number are about ten times more 

 abundant in the surface of the earth than 

 those which are odd. Also, all of the five 

 unknown elements, eka-ceesium, eka-manga- 

 nese 1, eka-manganese 2 (dwi-manganese), 

 eka-iodine and eka-neodymium, have odd 

 atomic numbers. It should be mentioned 

 in this connection, however, that there is 

 some doubt as to whether element 72 has 

 been discovered. 



"While the relative abundance of the ele- 

 ments in the lithosphere is undoubtedly 

 much affected by differentiation, there is 

 one group whose members are so closely 

 similar in chemical and physical proper- 

 ties, that they would be much less affected 

 in this way than any other elements. These 

 are the rare earths. The only difficulty in 

 this connection is that of making an accu- 

 rate estimate of the relative abundance. 

 In this the writer has been assisted by Pro- 

 fessors C. James and C. "W. Balke, but any 

 errors in the estimate should not be attrib- 

 uted to them. In the table, which includes 

 beside the rare earths a number of elements 

 adjacent to them, the letter c indicates com- 

 mon in comparison with the adjacent ele- 



ments, and r represents rare, ccc repre- 

 sents a relatively very common element, etc. 

 The comparison is only a very rough one, 

 but it indicates that the even-numbered 

 elements are in general more abundant 

 than the odd-numbered ones which are ad- 

 jacent. 



TABLE V 



The Predominance of Even-numbered Elements 

 Among the Bare Earths 



The above results may be summarized in 

 the statement that in the formation of 



THE ELEMENTS MUCH MOEE MATERIAL HAS 

 GONE INTO THE ELEMENTS OF EVEN ATOMIC 

 NUMBER THAN INTO THOSE WHICH ARE ODD, 



either because the odd-numbered elements 

 are the less stable, or because some constit- 

 uent essential to their formation was not 

 sufficiently abundant, or as the result of 

 both causes. 



It is easy to see, too, that in the evolu- 

 tion of the elements, the elements of low 

 atomic number and low atomic weight have 

 been formed almost exclusively, and this 

 indicates either that the lighter atoms are 

 more stable than those which are heavier, 

 or else that the lighter atoms were the first 

 to get the material, and their stability was 

 at least sufficient to hold it. 



It is possible that the heavier atoms have 

 been formed in larger amounts than now 

 exist, and that their abundance has been 

 reduced by atomic disintegration. It is of 

 course evident that the radio-active ele- 

 ments are now disintegrating, but the radio- 

 active series of elements includes only those 

 of atomic number 81 (thallium) to 92 



