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CHEMISTRY: W. D. HARKINS 
bered elements has been shown to be wHe', which may be written w(4H')'. 
Now, since the formula for the odd nimibered elements is wHe'+H's, 
or fj(4H')+H3^ it is evident that, if the supply of H3 needed by the 
elements was relatively small at the time of their formation, not so much 
material would go into this system. This would be true whether the H3 
represents three atoms of hydrogen or one atom of some other element. 
With regard to the latter alternative, it is at least remarkable that the H3 
occurs 11 times in the system for the first 27 elements, while H2 and 
H each occur only once, and it may also be mentioned that Fabry and 
Buisson^ have by interference methods determined the atomic weight 
of nebulium to be 2.7, and this they think indicates that its real atomic 
weight is 3. Also, Campbell^ has found that in the nebula N. G. C.^ 
Index 418, situated in the southern part of the constellation of Orion, 
the nebuHum spectrum is foimd farther from the interior than that of 
helium, while the hydrogen spectrum extends out to a much greater 
distance still. This, he thinks, indicates that the atomic weight of 
nebulium lies between the values for hydrogen (1) and helium (4). 
In studying the relative abundance of the elements the ideal method 
would be to sample one or more solar systems at the desired stage of 
evolution, and to make a quantitative analysis for all of the 92 elements 
of the ordinary system. Since this is impossible, even in case of the earth, 
it might be considered that sufficiently good data could be obtained 
from the earth's crust, or the lithosphere. However, 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. 
At least it might seem proper to assume that the meteorites would not 
exhibit any special fondness for the even numbered elements in com- 
parison with the odd, or vice versa, any more than the earth or the sun 
as a whole, at least not unless there is an important difference between 
these two systems of elements, which is just what it is desired to prove. 
A preKminary study of the most recent analyses of meteorites of dif- 
ferent classes showed that, either for any one class or for the meteorites 
as a whole the even numbered or helium system elements are very much more 
abundant than those of the odd numbered or lithium system. For a more 
detailed study use was made of the data collected by Farrington,^ who 
suggests that the average composition of meteorites may represent the 
composition of the earth as a whole. 
The results obtained by averaging the analyses of 318 iron and 125 
stone meteorites, 443 in all, show that the first seven elements in order of 
abundance are iron, nickel, silicon, magnesium, sulphur, and calcium; 
