22 JOURNAL OF THE 
ever, is always in a condition to take up additional atoms until 
its highest equilibrium is reached and in doing this it proceeds 
by the regular steps needed for bringing about a harmony of 
motion. A molecule in a lower state of equilibrium we have 
become accustomed to call unsaturated, calling that one satu- 
rated which is in its highest state of equilibrium. The fur- 
ther application of this hypothesis is easily made and need 
not be dwelt upon here, It will be helpful in many ways. 
This theory of valence makes it clear why it should vary 
toward the same element under different conditions. It is also 
clear that it might vary towards different elements as these 
are very possibly possessed of different motions. It is further 
evident that it is in accord with the conclusion that valence is 
not an inherent property of the individuai atom but is the re- 
sultant of the influence upon each other of the combining 
atoms, 
Only one point remains to be considered: Why do the. ele- 
ments of the same group have practically the same valence? 
The nearest answer to this, and it seems satisfactory, is that 
they are all possessed of the same phase or kind of motion. In 
other words the natural division into periods gives us seven or 
eight more or less different phases. These are, in large meas- 
ure, independent of the atomic weight. And so the elements 
in any given group have the same tendency towards similar 
states of equilibrium in forming compounds with any other ele- 
ment, as hydrogen or oxygen. Some elements, as copper, 
mercury, tin, etc., are peculiar in that they may change their 
phase of motion under certain influences, acting then as if 
they belonged to different groups and entering into totally 
different states of equilibrium in forming their compounds, 
Lastly it is possible for a combination of atoms of different 
elements, as NH* or CN, to have such molecular and intra- 
molecular motion that, although not in a state of equilibrium 
themselves, they are capable of entering into such states just 
as the single atoms of elements do, having apparently similar 
valence. 
I might develop this theory much further but it is unneces- 
sary now. Enough has been said to show that such an appli- 
