ELISHA MITCHELL SCIENTIFIC SOCIETY pT 
Again, the fact that certain groups of associated atoms be- 
have as one element and closely resemble known elements 
may be taken as a clue to the nature of the elements. Thus 
carbon and nitrogen, in the form of cyanogen, behave very 
much like the halogens; and nitrogen and hydrogen in the 
form of ammonia so closely resemble the group of elements 
known as the alkalies that this ‘‘volatile alkali” was classed 
with them before the era of our elements and the analogy 
lead to a vain search for an ‘‘alkalizing principle” and later 
to an equally futile pursuit of the metal ammonium. 
A further clue to this nature is afforded in the remarkable 
changes of properties which can be brought about in some 
elements by ordinary means, and one might mention the 
equally remarkable veiling of properties induced by the com- 
bining of two or more atoms. Thus copper exists in a cu- 
prous and a cupric condition, and the change from one to the 
other can be readily brought about. And this is true of 
many other elements. 
This has doubtless been a tedious enumeration to you of 
well-known facts and arguments, but it has been necessary, 
for I wish to lead you to the summing-up of these arguments 
and to induce you to draw boldly the necessary deductions. 
It is high time for chemists to formulate their opinions in 
this matter. It would seem as if we were shut up to one or 
two conclusions. Either these imagined simple bodies are 
after all compounds, built up of two or more common constit- 
uents, or they are but varying forms of one and the same 
kind of matter subjected to different influences and conditions. 
The supposition that they are distinct and unrelated simple 
bodies is, of course, a third alternative, but to my mind this 
is no longer tenable. 
The second hypothesis is the one put forth by Graham. It 
was his cherished vision of the gaseous particles about which 
he thought so deeply, andinmany ways sotruly. Thorpe has 
written of this as follows (loc. cit. 222): 
‘‘He conceives that the various kinds of matter, now rec- 
ognized as different elementary substances, may possess one 
and the same ultimate or atomic molecule existing in differ- 
ent conditions of movement. Graham traces the harmony 
