Ill 
THE NEW CHEMISTRY, A DEVELOPMENT OF 
THE OLD. 
By M. M. PATTISON MTJIK, M.A., F.B.S.E. 
I N a paper published in this Review (January 1878), I 
endeavoured shortly to summarize the more important 
differences between that system of chemistry which was 
founded on a so-called equivalent notation, and the modern, 
or atomic phase of the science. 
The general conclusion to which that summary led was, 
that the old chemistry was empiric, whilst the new is scientific ; 
but, as was there remarked, empiricism precedes science : 
science is the natural development of empirical statements, and 
is not to be regarded as entirely a new departure. 
Believing, as I do, that the old and new chemistry are 
essentially opposed in their methods, I nevertheless am certain 
that the germs, at least, of many of our modern chemical 
theories are to be found in the statements, and even in the 
hypotheses, of the workers of half a century since : and in the 
present paper I propose to trace, in a little detail, what I 
believe to be a correct outline of the development of two of 
the more important theories of modern chemistry.* 
The chemical views most in vogue before the strictly 
modern epoch, were founded more on considerations of the com- 
position of compounds than on the actions of these compounds. 
Dumas introduced wider views by recalling the attention of 
chemists to the fact that in order to frame even a tolerably 
complete system of classification, an answer must be given to 
the question, ‘What does this substance do V no less than to 
the other question, ‘ Of what is this substance composed ? ’ 
* In the paper referred to, I briefly sketched the history of the develop- 
ment of the older doctrine of ‘ Eq uivalents ’ into the modern hypothesis of 
‘ Valency.’ 
