Evolution and Devolution of the Elements. 25 
The same considerations apply to group II. i£ it be sub- 
divided as follows : — A. Beryllium, magnesium, calcium, 
strontium, barium, radium ; and B. zinc, cadmium, mercury. 
However, in chemical properties there is a certain relationship 
between the two sub-groups. 
In group III., though the members o£ the different sub- 
groups occupy different positions on the two curves mentioned 
above, yet their chemical properties are more closely connected 
than those of group II. If we proceed in this manner through 
the groups, we shall in all cases find the members of corre- 
sponding sub-groups differing with regard to their positions 
on the curves, and varying the closeness of their chemical 
relations as they pass from group to group. In groups 3, 1, 
and 5 the members are most alike, while those in groups 1 
and 7 are most dissimilar. 
To account for these facts we venture to put forward the 
following explanation. We would suggest that members of 
each sub-group evolve in turn from the first member of that 
group, and resemble each other in structure. All the 
members of a single Mendeleeff group do not evolve from 
each other in order of atomic weight, but only each sub- 
group, the two sub-groups of each column have an entirely 
different internal atomic structure, their apparent resemblance 
being wholly due to a similarity in the external form of their 
atoms. This question will be more fully discussed later, but 
at present we must investigate the result this assumption will 
have on the form of the periodic table. 
In the first place, it is evident that if each sub-group be 
considered as being the result of a separate and distinct 
process of evolution, an increase in the number of sub-groups 
must be made. To determine what the number shall be, it is 
best to consult the atomic volume curve. It is generally 
admitted that lithium, sodium, potassium, and rubidium are 
typical members of one family, as is clearly shown by their 
positions on the above-mentioned curve. Between lithium 
and sodium are seven elements, and the same number is found 
between sodium and potassium, but between potassium and 
rubidium there are seventeen. This means that in the hori- 
zontal series, starting with lithium and sodium, there are 
eight groups, but in the next series this number has increased. 
An explanation of this is that one or more of the elements in 
the second series of eight has developed in more than one way. 
Lest this seem improbable, we may mention that it is 
exceedingly unlikely that there are more than four original 
elements or protons, while it is universally acknowledged 
that the series starting with lithium and sodium both contain 
