108 BELL SYSTEM TECHNICAL JOURNAL 



Interesting as are the chemical and physical properties of deuterium 

 and its compounds, we are here concerned only with the nucleus of the 

 H^ atom, the deuton (all the other suggested names seem to be fading 

 out). The accepted value for its mass is that given by Bainbridge, 

 2.0131 on the standard scale in which the mass of the O^^ atom is 

 16 exactly. Of its spin I shall speak in a later article. Its powers of 

 transmutation are remarkable, and quite unlike those of H^; if first a 

 beam of H^ nuclei (protons) and then an equal beam of deutons be 

 directed against targets of various elements, the number of fragments 

 observed per unit time is greater for some elements and less for others, 

 and their ranges in general are different. In some cases it seems possible 

 that the deutons themselves are being split into protons and neutrons, 

 a result of great importance if it can be established beyond question. 

 We shall consider the data at length. 



The neutron 



Most of what has newly been learned about the neutron will find 

 appropriate places elsewhere in this article. There should be a 

 separate section about the deflections suffered by neutrons when they 

 impinge on or pass close to nuclei without transmuting them — the 

 topic known as "scattering," "interception," or (badly) "absorption" 

 of neutrons. This topic however is scarcely ripe for description in 

 such an article as this, the experiments being difficult and the in- 

 ferences from the data being highly controversial. I therefore post- 

 pone it to some future occasion, remarking only that it seems established 

 that a neutron may pass within a very short distance indeed from a 

 nucleus — only a very few times 10~^^ cm from the centre thereof — 

 without interacting with that nucleus in any perceptible way. 



Masses of the Lighter Atoms 



There are now thirteen of the lighter atoms of which the masses — 

 in terms of the mass of the O'^ atom taken as 16 exactly — have been 

 determined to four and even to five significant figures. Most of these 

 values were mentioned in the First Part, but it will be convenient to 

 have them all tabulated here. They are the masses of complete 

 atoms, nuclei accompanied by their full quotas of orbital electrons. 

 The uncertainties quoted are the "probable errors"; where Aston 

 originally gave the maximum" possible uncertainty, this has been 

 divided by 3 (see First Part, footnote 10). Values marked with an 

 asterisk are from Bainbridge, the others from Aston; the value for H^ 

 has been obtained by both. 



