330 Prof. W. D. Harkins on the 



zero and some unknown limit which is probably not greater 

 than 07, unless in some very exceptional cases. The 

 maximum value for any known atomic species is that of 

 0612 for Ha B. 



In many respects this plot is similar to that given in 

 fig. 1 (PI. XII.), so the description need not be repeated, but 

 it may be noted that the line of maximum stability is here 

 represented by a curve tangent to the M axis at the origin, 

 which has the general form of an hyperbola. In the upper 

 part of the plot an enlarged diagram for the light atoms is 

 presented. 



The figure indicates that Br 35 9 79 and As 33 9 75 ; Bi^ 



81 

 1 



and Kr 36 n 83 ; I 53 21 127 and X 54 2l 129 , are pairs of atomic 

 species with the same isotopic number, but only in the first 

 of these pairs could one of the two be either an alpha 

 disintegration or aggregation product of the other, since in 

 only this one case does the nuclear charge differ by 2 and 

 the atomic weight by 4. 



The plot which represents the atomic weight P as a 

 function of the atomic number Misgiven in fig. 6 (PI. XI L). 

 The straight line in the main plot has a slope of 2 in terms 

 of the coordinates, which represents the principal term in 

 the atomic weight equation 



P = 2M. 



In no case is the atomic weight less than that represented by 

 this simple equation, but it increases above this value as the 

 isotopic number increases. The radioactive series are repre- 

 sented in an enlarged diagram in the upper left-hand 

 corner. 



Electron-Proton Groups concerned in the Building 

 of Complex Nuclei. 



(Atomic weights 4, 3, 2, and 1.) 

 While the present paper up to this point has concerned 

 itself almost entirely with the general relations of the 

 positive and negative electrons in atom nuclei without 

 reference to their possible grouping, considerable evidence 

 has appeared in the plots and in the considerations con- 

 cerning the isotopic and class numbers, which makes it 

 evident that any complete treatment must give very careful 

 attention to such groupings. 



If, as an example of a heavy nucleus, that of thorium is 

 considered, it is seen that it probably contains 232 positive, 

 and 142 negative, electrons, or 374 particles in all. This 

 number is so great that it seems altogether improbable that 



