584 SCIENCE PROGRESS 



be less fanciful to start from the evidence of radioactive changes, 

 which, many years ago, showed that the a-particle or helium ion 

 is certainly one such primordial material constituent common 

 to the atoms of all the radio-elements. But to prefer to regard 

 the atom of negative electricity as the primordial atom of matter 

 seems to be a relic of an earlier confusion between electricity 

 and matter that the facts, if not the language of science, have 

 long outgrown. 



One gets into closer touch with reality in the recent 

 determinations of the number of electrons present in the atom 

 and in the conclusion that in each atom this number is approxi- 

 mately one-half of the atomic weight. The scattering of X-rays 

 by the electrons in the atom we find likened, in a manner that 

 will be helpful to those unable to follow the reasoning, to the 

 scattering of ordinary light by the molecules of air, which 

 produces the blue of the sky, and like the latter method has 

 been found useful to determine the number of scattering points 

 through which the beam passes. Sir Ernest Rutherford's 

 determination of the value of the positive charge of the central 

 nucleus of the atom by the scattering or deflection of the a-rays 

 confirms the aforementioned result. However, these methods 

 and also the later and more refined one of Moseley on the 

 precise Atomic Number are at fault in one not unimportant 

 respect. They can only reveal the outer electrons of the atom. 

 They cannot reveal the electrons in a central concentrated 

 nucleus where their charge is merged in that of a superior 

 positive charge. Of these nuclear electrons, as of so much that 

 is fundamentally new about atomic structure, we have learned 

 only by radioactive change. Their precise number is vague, 

 and though not necessarily large, they are of interest in that 

 they alone are entitled to be considered primordial constituents 

 of the atom in the Proutian sense. A glass rod is rubbed. Do 

 the atoms of matter therein suffer transmutation ? If they 

 do not, how can the electrons which have been removed by 

 the rubbing be regarded as primordial constituents ? Again, 

 the hydrogen atom loses its electron and becomes a hydrogen 

 ion. Is this a transmutational change ? If not, why speak of the 

 electron in question as a primordial constituent ? But in radio- 

 active changes, not only the changes effected by the expulsion 

 of the material a-particles, but also those effected by the 

 expulsion of /3-particles, or negative electrons, are equally 



