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chosen as a point for the restriction of our views of the properties of the others — 
where only the qualities found in the first are to he measured out to the rest. 
I shall now proceed to inquire how its more thorough application tends to the 
development of a rational chemical theory. 
It has been found that there is one leading feature, one inherent property, 
common to all the elements. It has been denominated chemical affinity. It is 
discovered under two aspects : — (1) affinity of kind ; (2) affinity of degree. 
Affinity of kind is the special affinities manifested among the elements, the one 
for the other, etc., as carbon for oxygen, for chlorine, for hydrogen, etc. 
Affinity of degree is the grades, or also limits of combination, which the elements 
display. For instance, C 2 0 2 and C 2 0 4 are the degrees of affinity of carbon for 
oxygen. C 2 0 2 may he called the first degree, and C 2 0 4 may he termed the second 
degree, and, as a higher degree than this is not known for carbon, its ultimate 
affinity or combining limit. Affinity of degree in an element may have only one 
grade. It may have, however, and generally has more than one. Here then is an 
inherent property common to all elements, by the removal of which the chemical 
character of an element will be destroyed, and by virtue of which an element finds 
its place marked out in a complex body. 
It is such a property that is required to form the base of a system. Nor would 
its suitableness for this purpose be affected by the discovery that the elements are 
themselves composite bodies, which view the chemist is perhaps not unwarranted to 
adopt. For, in such a case, the necessity would doubtless still be found to exist of 
adopting the principle of affinity, or something at least equivalent to it, as the basis 
of the explanation of chemical combinates. In applying this method, I propose at 
present to consider the single element carbon. This body is found to have two 
highly distinguishing characteristics : — 
1. It combines with equal numbers of hydrogen, chlorine, oxygen, sulphur, etc. 
2. It enters into chemical union with itself. 
These two properties, in my opinion, explain all that is characteristic of organic 
chemistry. This will be rendered apparent as I advance. 
This second property is, so far as I am aware, here signalized for the first time. 
Evidence as to its being a property of carbon may therefore be required. 
It will be found in the following : — What is the link which binds together bodies 
composed of 4, 6, 8, 10, 12, etc., equivalents of carbon, and as many equivalents of 
hydrogen, oxygen, etc. ? In these you may remove perhaps all the hydrogen or 
oxygen, and substitute so many equivalents of chlorine, etc. It is then the carbon 
that is united to carbon. Further, that it is not the hydrogen that is the binding 
element in these combinates is evident ; thus — 
