NO. II STRUCTURE OF THE ATOM PARSON 49 



spheres, or are acting largely between them, and so the average 

 volume per magneton should be about the same in the two cases. 

 If there is any difference at all between the two cases, it is that the 

 cluster in which the forces between atoms are considerable will be 

 compressed even less than the other; because it is rarely possible 

 for valence magnetons to reach a state of such low magnetic energy 

 as exists in an atom where the magnetic, forces are acting almost 

 entirely within the atom owing to all its magnetons being in groups 



of eight. Even in the case of a molecule like H-fCy, where it is 



true that all the magnetons are in groups of eight, the electrostatic 

 strain must increase their magnetic energy and expand the groups 

 somewhat. 



This theoretical result is of course directly at variance with the 

 facts. A cluster of atoms of Argon (3-y) or of Krypton (5y) has 

 about four times the volume per magneton of a cluster of Iron, Co- 

 balt, or Nickel atoms (3y + 8) ; and a similar relation holds between 

 Helium atoms (y) and Carbon atoms (y + 4). The great decrease 

 in volume that is undoubtedly caused by an increase of the magnetic 

 forces between the atoms at the expense of the magnetic forces 

 within the atoms is much more than a filling in of " spaces " could 

 account for, and can have only one explanation : the positive sphere 

 must have a much lower charge density and a much greater com- 

 pressibility at its boundary than in its interior; and thus the com- 

 pression of this boundary layer, since it is due to the action of the 

 valence magnetons chiefly, is found to be a " periodic " effect as the 

 atomic weight increases. 



/ ^\ cUfrfa/ncg. 



This boundary layer, which I shall call the envelope of the atom, 

 will be assumed to exist quite independently of the action of mag- 

 netons upon the positive sphere, and may reasonably be supposed to 

 4 



