1815.] On Dalion’s Theory of Chemical Composition. 377 
than it would be if A were at E, in the ratioof D Eto DA; and 
by the composition of forces, it will be less in the direction of C A 
than in that of D A, in the ratioof AF to AC. But ADE and 
FAC being similar triangles, AC: AF::DE:DA. The re- 
pulsion of A from D, in the direction C A, will therefore be the 
same at whatever point in the circle A be placed ; and the repulsion 
of A from B in the direction C A being the same also, each of the 
three atoms A, B, D, will be repelled from C with twice as much 
force as when only two atoms are united to C. For the same 
reason, when four atoms are united to C, they will be repelled with 
three times as much force; and so on for any greater number of 
atoms united to C. 
2. In chemical compounds it is generally, if not universally, 
observed, that an increase of specific gravity isa consequence of 
chemical union ; and the specific gravity of carbonic acid being 
greater than that of carbonic oxide, we cannot consistently suppose 
the latter to be twice, and the former only once, compounded. 
3. It rarely happens that bodies of low oxidation are acid, and 
those of high oxidation not acid. The first combination of a bod 
with oxygen produces an oxide; and it is not till-a second or third 
addition of oxygen is made that the characters of an acid are found 
in the compound. We cannot, therefore, consistently suppose car- 
bonic acid to be the first, and carbonic oxide the second, combina- 
tion of oxygen with carbon. 
4. In comparing the various compositions of. carbon with othe 
elements, Mr. Dalton finds that the combinations of the different 
atoms would be much more complicated, as well as inconsistent with 
each other, if the relative weight of an atom of carbon were sup- 
posed to be 2°8 instead of 5°6. 
It is obvious, indeed, that the agreements, which Mr. Dalton has 
pointed out, cannot be explained by any arbitrary assumption of the 
relative weights of the ultimate divisions’ of chemical elements, 
which enter into composition with each other. 
The same reasoning applies to all compounds where the same 
agreements are observed ; and the number of these, established by 
some of the best chemists of the present and former times, is so 
great that it is not easy to refuse assent to the generalization of Mr. 
Dalton’s principle of chemical composition. 
It is true there are several compounds which appear to be at 
variance with this principle. But if we consider the extreme diffi- 
culty of separating the elements of some chemical compounds, and 
the uncertainty which must in many cases remain respecting what is 
or is not elementary, we cannot in the present state of the science 
reasonably expect all the appearances to be distinctly explained. 
When these things are considered, 1 think it is most to be won- 
dered that there are so few apparent exceptions to the law which has 
been unfolded by Mr. Dalton. 
This principle, and the facts on which It is founded, are directly 
