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Proceedings of the Royal Society of Edinburgh. [Sess. 
It is impossible here to enter upon any extensive criticism of this theory. I can 
only remark that it is not merely an unprofitable figure of language, but is injurious 
to science, inasmuch as it tends to arrest scientific inquiry by adopting the notion 
that these quasi elements contain some unknown and ultimate power which it is 
impossible to explain. It stifles inquiry at the very point where an explanation is 
demanded, by putting the seal of elements, of ultimate powers, on bodies which are 
known to be anything but this. 
Science demands the strict adherence to a principle in direct contradiction to 
this view. That first principle, without which research cannot advance a step, dare 
not be ignored ; namely, that a whole is simply a derivative of its parts. As a con- 
sequence of this, it follows that it is absolutely necessary to scientific unity and 
research to consider these bodies as entirely derivative, and as containing no 
secret ultimate power whatever, and that the properties which these so-called quasi 
elements possess are a direct consequence of the properties of the individual ele- 
ments of which they are made up. 
Nor is the doctrine of bodies being “ conjugated by addition ” a whit in advance of 
that which I have just been considering. This doctrine adopts the simple expedient 
of dividing certain combinates, if possible, into two imaginary parts, of which one 
or both are bodies already known. Then it tells us that these two parts are found 
united in this body. But how they are united, or what force binds them together, 
it does not inquire. Is this explication arbitrary? Is it instructive? Is it science ? 
I may now be permitted to submit a few considerations relative to a more 
rational theory of chemical combination. 
As everything depends upon the method of research employed, it will in the 
first place be necessary to find one that may be relied upon. If the method is good, 
and conscientiously carried out, stable and satisfactory results may be expected. 
If, on the contrary, it is vicious, we can only expect a corresponding issue. A satis- 
factory method is, however, not difficult to find, nor is it difficult in its application. 
The principle which ought to guide all research is in every case the same. It is 
that of analysing till it is impossible to reach more simple elements, and of studying 
these elements in all their properties and powers. When all the properties and 
powers of the individual elements are known, then it will be possible to know the 
constitution of the combinates which their synthesis produces. It is necessary 
therefore in chemical research, in order to ascertain the various qualities and 
functions of the different elements, — 
1. To consider the whole of chemistry as one. 
2. To take into consideration every known combinate, and to study the character, 
functions, and properties displayed by each element for itself, in each of these com- 
binates in all their different conditions and aspects It is by a comparison of the 
different bodies among themselves that we are able to trace the part that is per- 
formed by each element separately. 
3. To trace the general principles common to all the elements, noting the special 
properties of each. 
This method is essentially different from that where one class of bodies is 
