296 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 13 



For the elements below the radioactive group, that is, those of 

 lower atomic weight, some evidence of instability has recently been 

 obtained. Rutherford, by passing swiftly moving alpha rays through 

 nitrogen, has observ^ed a slight evolution of hydrogen, an indication 

 that hydrogen is a constituent of the heavier and more complex 

 element. Oxygen, treated in the same way, yields a product of 

 different character, something which appears to have an atomic 

 weight near 3. If, however, the value should be slightly lower, it 

 would have a curious significance. Attention has already been 

 called to the existence of nebulium, to which the atomic weight 2.7 

 has been provisionally assigned. This is very close to 2.666..., or 

 2 ^/a more precisely. 



Now 2 Vs X 6 = 16, the atomic weight of oxygen, a relation 

 which may possibly be experimentally verified. If the bombardment 

 of oxygen were carried on for a long time it might yield a gas in which 

 the spectral lines of nebulium could be detected ; and if that were 

 done it would be a step forward in the study of the atoms. I offer 

 this suggestion with some hesitation, but it seems to be worth con- 

 sidering. It affects a number of other elements of which the atomic 

 weights are multiples of 16. 



By a remarkable series of experiments F. W. Aston^ has obtained 

 evidence which he regards as proof of the complexity of the atomic 

 weights as determined by chemical methods. Powerful positive 

 rays in a magnetic field were applied to a number of elements, which 

 then gave what he terms their "mass spectra." These spectra show 

 lines corresponding to whole number atomic weights, which represent, 

 not the accepted values, but some higher and some lower. Chlorine 

 gives two such lines, corresponding to atomic weights 35 and 37, 

 and mercury gives at least six, ranging from 197 to 204. The last 

 two figures, I may add, are near the atomic weights of gold and thal- 

 lium, that of mercury being 200.6. These new lines, as interpreted 

 by Aston, represent isotopes, and the accepted atomic weights are 

 regarded as mere statistical averages. In other words the atomic 

 weights known to chemistry relate to mixtures, and are not true 

 constants. 



I must here allow myself to indulge in a very obvious truism. 

 Whenever new phenomena are discovered an attempt is made to 

 interpret them, and to bring them into relations with other phenomena. 

 i 'Science Progress 15:212. 1920. 



