24 Messrs. A. C. and A. E. Jessup on the 
fact, we may go so far as to say that the whole process of 
evolution is entirely governed by the possibility of energy 
leaving the systems. 
The process of evolution may be considered to be a per- 
fectly smooth and continuous one, and the elements as we 
know them only to represent positions of maximum stability, 
which are arrived at during the process of evolution. Since 
the elements may be looked upon as denoting the positions of 
maximum stability or, so to speak, stopping places in the 
evolution process, we can readily comprehend the simul- 
taneous existence of all the elements. Of course the rate of 
evolution along different groups may vary, and therefore we 
are not surprised at the fact that calcium and iron, with 
atomic weights of 40 and 56 respectively, are found in stars 
which do not contain sodium with an atomic weight 
of 23. 
We will now turn our attention to the periodic table as 
given by Mendeleeff and see how far our ideas of evolution 
agree with the form of the table as given by him. Several 
attempts have been made to remodel this table, of which 
perhaps the most notable are the harmonic periods of Professor 
Emerson Reynolds, the vibrating pendulum of Sir William 
C Jrookes, and the logarithmic spiral of Dr. Johnstone Stoney. 
It is, however, admitted that there are defects in all of these, 
and we hope to be able to remove some of them. We may 
perhaps here mention that the idea of evolution in groups was 
first suggested by MendeleefFs table, and that without it our 
original observations would not have developed. It was only 
when we came to extend our ideas that we found that they 
would not entirely agree with the table as it originally stood. 
Consequently, we have in our turn ventured to present the 
table in a modified form, which w r e hope may smooth over 
some of the difficulties at present connected with the classical 
researches of the great Russian. 
In the table as it now stands, it is customary to divide the 
main groups into two sub-groups. For instance, group I. 
is in Mendeleeff' s table divided into group I A. hydrogen, 
lithium, sodium, potassium, rubidium, and csesium ; and 
group I B. copper, silver, and gold. 
Now, it will at once be seen that although all the elements 
of the same sub-group resemble each other greatly, yet 
members of different sub-groups have apparently very little 
connexion between them. Members of the same sub-group 
occupy corresponding positions on the atomic volume and 
melting-point curves, while the positions of members of 
different sub-groups differ very widely. 
