34 Messrs. A. C. and A. E. Jessup on the 
can evolve normally until the first position o£ maximum 
stability is reached — carbon. It follows from this, therefore, 
that the formation of these distorted rings (or in other words 
" indirect evolution ") only first becomes possible with 
trivalent elements, and that it is very likely to take place 
with tetravalent elements. We press this conclusion on the 
argument previously developed, that a tetravalent element 
will be still less desirous of completing the system of eight 
electrons than even a trivalent element. As a natural sequence 
of this, we should expect to find that the element silicon would 
show an exceptional tendency towards this phenomenon of 
indirect evolution, and, as a matter of fact, as we have already 
shown, the element silicon gives rise to a great number of 
indirect derivatives. It is important to notice that neither 
of the elements proto-boron or silicon gives only one series of 
indirect derivatives, for in the former case we have in addition 
to carbon the elements nitrogen, oxygen, and fluorine ; and 
in the latter case we have vanadium, chromium, and man- 
ganese. We are convinced that there is some fundamental 
reason underlying the production in this way of several 
indirect derivatives. Taking the case of the indirect evolution 
from the element proto-boron, it will be seen that we have 
derived in this way the elements carbon, nitrogen, oxygen, 
and fluorine ; that is to say, a tetravalent, a pentavalent, a 
hexavalent, and a heptavalent element. 
In speaking of the valency of an element we define this as 
the number of electrons which that element gives up in 
entering into combination : thus lithium is monovalent, 
beryllium is divalent ; nitrogen is pentavalent, because it 
gives up five electrons ; so that we speak of nitrogen, 
oxygen, and fluorine as being penta-, hexa-, and hepta-valent 
respectively. 
Now we have already shown that in the case of the element 
carbon, the formation of this element is caused by the 
absorption of a number of the sets of eight electrons which 
in themselves are insufficient to form a complete ring. The 
result is that the distorted tetravalent ring which gives rise 
to carbon is formed ; and furthermore, the three free electrons 
on the outer ring of the antecedent element have not taken 
up five electrons to form a set of eight, but only four. In the 
case of the element nitrogen an almost identical procedure 
takes place, only in this case three electrons have been 
extracted in place of the normal five, with the result that a 
second type of distorted ring is produced with a valency 
of five. 
In the case of the element oxygen a similar absorption of 
