6 JOURNAL OF THE 
Elements, p. 31): ‘The name copper is used to distinguish a 
certain group of properties, that we always find associated 
together, from other groups of associated properties, and if 
we do not find the group of properties connoted by the term 
copper we do not find copper.” 
These properties are exhibited by the action of a small 
group of forces. Perhaps we do not know all of the forces; 
certain it is that we do not accurately know all of the proper- 
ties, but, to quote Patterson-Muir again: ‘‘The discovery of 
new properties always associated with a group of properties 
we call copper would not invalidate the statement that cop- 
per is always copper.” 
The properties of an atom are either primary, inherent and 
as unchanging as the atom itself, or they are secondary and 
dependent upon the influence of the other atoms, or varying 
with the change of conditions. To the first class belong such 
properties as the atomic weight, atomic heat, specific grav- 
ity, etc.; to the second, chemical affinity, valence, etc. Inall 
the study of the atom the distinction between these should be 
carefully mainta:ned in order that there may be clear think- 
ing. 
There is no field of mental activity requiring more faith 
than that of the chemist. He is dealing with the ‘evidences 
of things unseen.’ He must not be content with the mere 
gathering of facts, but divine what he can of their deeper 
meaning. Kew chemists have had such insight as Graham 
into the significance of even the simplest changes. He was 
not content with mere surface observation. Even the com- 
monest phenomena were to him full of meaning as to the 
atoms and their ‘eternal motion.’ ‘Thorpe (Essays in Histor- 
ical Chemistry, p. 219) has drawn afresh the attention of the 
chemists to the thoughtful words of this great thinker. His 
mind was filled with the fascinating dream of the unity of 
matter. ‘‘In all his work,” says Adam Smith, ‘‘we find him 
steadily thinking on the ultimate composition of bodies. He 
searches after it in following the molecules of gases when 
diffusing; these he watches as they flow into a vacuum or in- 
to other gases, and observes carefully as they pass through 
