446 On the Cause of Chemical Proportions. [Dec. 



considering. I shall state some of these cases, without, how- 

 ever, considering them as ahsolute proofs against the hypothesis, 

 hut rather as difficulties which we must endeavour to surmount, 

 in order to obtain a clear and well established theory of chemical 

 proportions. 



1 shall begin with a short explanation of the corpuscular 

 theory, such as I conceive it. 1 shall employ the word atoms to 

 signify the corpuscles, or smallest parts of which bodies are 

 composed. When I say the smallest parts, I mean that they 

 cannot be divided into other parts still smaller. I do not enter 

 into any discussion whether matter be infinitely divisible or not, 

 but take it for granted that an atom is mechanically indivisible; 

 and of course that a fraction of an atom cannot exist. 1 suppose 

 likewise that atoms are all spherical, and that they have all the 

 same size. (This last circumstance is not necessarily attached to 

 the idea of atoms, but it is absolutely necessary if regular 

 figures are to result from their union, and if they unite in defi- 

 nite proportions, even in the most complicated combinations). 

 It appears likewise necessary that when an atom of the body, A, 

 combines with one or more atoms of the body B, to form a new 

 compound atom, the atom of A touches each of the atoms of 

 B. Hence a compound atom is formed by the juxtaposition of 

 several elementary atoms ; just as an aggregate is formed by the 

 juxtaposition of different homogeneous atoms. But the differ- 

 ence consists in this, that in the first case an electric discharge 

 takes place of the specilic polarity of the heterogeneous atoms, 

 which cannot take place between homogeneous atoms. (See my 

 conjectures on this subject in Nicholson's Journal for March, 

 1813, p. 154.) 



A compound atom, for very obvious reasons, cannot be con- 

 sidered as spherical; but as it is composed of atbrfts mechanically 

 indivisible, or which cannot be separated by mechanical means, 

 the compound atom is justly as completely mechanically indivi- 

 sible as the elementary atom. It is likewise evident that an atom 

 composed of A + 3 B ought to be greater, a 'id to have a diffe- 

 rent figure from an atom composed of A + B. The former 

 ought to have the form of a triangular and equilateral pyramid, 

 while the latter must have a linear form. 



We may divide the atoms into two classes : 1. Elementary 

 atoms : 2. Compound atoms. The compound atoms are of 

 three different species; namely, 1. Atoms formed of two ele- 

 mentary substances united. We shall call them compound atoms 

 of the first order, 2. Atoms composed of more than two elemen- 

 tary substances: and as these are c. rad in organic bodies, 

 or bodies obtained by the destruction of such organic matter, 

 we shall call them organic atoms. 3. Atoms formed by the union 

 of two or more compound atoms, as, for example, the salts. 

 We shall call them compound atoms of the seco?id order. 



