372 On Dalion’s Theory of Chemical Compasition. [Nove 
composition, which he first observed only in a few instances, is 
found to prevail. * 
A small number of facts are sufficient to explain the nature of 
this principle ; and in the following it appears very distiuctly, 
Ist. 100 grains of olefiant gas contain 85 of carbon and 15 of 
hydrogen ; +. that.is, in the proportion of 5°6 carbon to 1 hydrogen. 
2d. 100 grains of carbonic oxide contain 44% carbon and 55+ 
oxygen; { that is, in the proportion of 5°6 carbon to 7 oxygen. 
3d. LOO grains of water contain 121 hydrogen and 87+ oxygen ; § 
that is, in the proportion of 1 hydrogen to 7 oxygen.. 
Ath. 100 grains of carbureted hydgogen contain. 74 carbon and 
26 hydrogen; || that is, in the proportion of 5°6 carbon to 2 
hydrogen. 
5th. 100 grains of carbonic acid contain 28-6 carbon and 71-4. 
oxygen ;** that is, in the proportion of 5-6 carbon to 14 oxygen,. 
Now it is very remarkable that the last terms, in the first and 
second of these proportions, are the same as the first and second. 
terms, representing the proportions of the same elements, in the 
third compound. 
In the fourth and fifth compounds we have a forther coincidence 
of adilferent kind. Here we have the same elements as in the two 
first compounds; and the last terms of the proportions in the first 
and second, multiplied by two, are respectively equal to the last 
terms of the fourth and fifth. 
'  Presuming that something more than an accidental. coincidence 
is indicated by such agreements as these, Mr. Dalton proposes to 
explain them as follows. — 
If we suppose the ultimate divisions, or atoms, which unite in 
chemical compounds of carbon, hydrogen, and oxygen, to be of 
different relative weights, in the proportion of 5°6, 1, and 7, we 
shall have equal numbers of atoms of each of their elements in 
each of the first three compounds ; and if the compounds’ be homo- 
geneous, each atom of carbon in the first compound must, be united 
-to an atom of hydrogen; and in the second, each atom of carbon 
must be united to an atom of oxygen; in.the third compound, each 
atom of hydrogen must be united toan atom of oxygen; each atom 
of carbon in the fourth compound must be united to two atoms of 
hydrogen; andin the fifth, each atom of carbon must be united to 
two atoms of oxygen. Upon this principle, then, we have the ex- 
# Itisnota little remarkable, that the labours of some-of the priacipal modern 
chemists in Eurepe, where quantity was the object of research, have given results. 
unifermly favourable to the establishment of this principle, though they haye been 
in some instances unacquainted withit. Witness those of Clement and Desormes,. 
Wollaston, Davy, Heary, Berthollet, Berard, Gay-Lussac, Berzelias, &c, &c, 
+ Thomson, Nich. Jour, xxviii. 352. Davy, 309. 
t Clement and Desormes, Ann. Chim. tom. 39. 
& Humbolt, Gay-Lussac, Ann. Chim. 1805. Nich. Jovr. xxx. 270,. 
» Henry, i. 355, a deduction, Davy, 307. 
e® Allen and Pepys. 
