Evolution (Did Devolution of the Elements. 29 
urge that in elementary evolution, the principle of heredity 
is an all-important one, unci that the normally derived elements 
would be characterized by the same properties as the ante- 
cedent elements in each case. Now, in the case of the 
lightest protou, hydrogen, its chemical behavour is that of a 
monovalent element ; and from our standpoint of the existence 
of the principle of heredity (see page 51), we consider that 
the direct descendants of hydrogen must be monovalent 
elements, or, in other words, that hydrogen must be the 
antecedent element of the alkali metals, and therefore we have 
placed hydrogen at the head of this family *. An exactly 
similar argument is applicable to the fourth proton helium, 
and we therefore place helium in the last group of our Table, 
thereby establishing it as the progenitor of the inactive 
gases. 
We now have left two protons, viz., those with wave- 
length 4959 and 5007 respectively. Clearly these two must 
in some way have given rise to all the elements except the 
alkali metals and the monovalent gases. In our table, 
we have placed the proton with wave-length 4959 at 
the head of the alkaline earth metals and the remaining 
proton at the head of the trivalent third group. Now 
inasmuch as we know at present nothing of the chemical 
properties of these two unknown elements, it is clearly 
impossible for us to make any definite statement as to how 
the evolution proceeded from them. Our reasons, however,, 
for placing these two elements in the positions assigned to 
them are as follows : — (1) Hydrogen has an atomic weight 
of one, helium of four. The wave-length of the hydrogen 
line is 4862, and that of the helium line is 5876. vVe there- 
fore assume that the element whose wave-length is 4959 has 
a smaller atomic weight than the element with wave-length 
5007. (2) Silicon gives rise to a great number of elements, 
many of which are to be found in considerable quantities, 
both in the earth and in the stars. It is only reasonable 
therefore to conclude from this that the original proton from 
* At first sight, it might be pointed out that hydrogen can be con- 
sidered as the progenitor of the halogen family, inasmuch as these 
elements are usually spoken of as being monovalent. Against this, how- 
ever, we point out that the monoyalency of the alkali metals is equal and 
opposite to that of the halogens. The former are monovalent in the fact 
that they have one free electron to be given up when entering into com- 
bination, while the latter are monovalent in the fact that they take up 
one electron in forming compounds. Hydrogen and the alkali metals 
are absolutely analogous in their compounds with the halogens. If 
hydrogen belonged to the halogen group, hydrogen should be more 
electro-negative than fluorine, and should form mono-atomic compounds 
with the alkali metals, more stable than the fluorides. 
