202 Dr. Macneven's Exposition of [Sept. 



reduction of their volume by cold, favours the idea of caloric 

 interposed between those particles being the cause of their not 

 coming in contact. 



15. If oxygen, hydrogen, and nitrogen gases be mixed in the 

 same vessel, and the electric spark passed through them, a com- 

 bination of oxygen and hydrogen takes place in preference to a 

 combination of oxygen and nitrogen. The reason seems to be 

 that there is a force of attraction or affinity inherent in eveiy 

 atom of matter, and that in different bodies it differs in intensity. 



16. When gases are made to unite, that gas which enters into 

 the compound in the smallest quantity in bulk is represented by 



1, and then the bulk of the other constituents of the compound is 1, 



2, 3, 4, &c. Here atoms and volumes are deemed to bear to 

 each other the same exact ratio, as we have distinctly found in 

 the example of oxygen and hydrogen gases. It is held that two 

 atoms of one substance do not unite to two atoms of another, for 

 this would resolve itself into atom to atom ; nor two of one to 

 three of another, which would amount to the union of an atom 

 of one substance to one and a half atom of another. This can- 

 not be, since the atom is indivisable. Were it possible to divide 

 atoms, or to form combinations with their fractional parts, the 

 compounds of various oxides would be so multifarious that all 

 traces of chemical proportion would disappear, or be only occa- 

 sional, whereas it is found to be perpetual and certain. 



17. Knowing the weight of an atom of oxygen and of an atom 

 of hydrogen, we have it in our power to determine the weight 

 of an atom of the other substances which unite with oxygen, or 

 with hydrogen, or with both. One hundred parts of sulphur 

 unite with two well known proportions of oxygen, the first con- 

 sisting of 100 oxygen, the second of 150 oxygen both in weight. 

 Here the proportions of oxygen being to each other as 1 : 1^-, or 

 as 2 : 3, it was reasonable to suppose that the first proportion 

 represented two atoms of oxygen, and the second of tluee atoms, 

 and that there was another compound consisting of one sulphur 

 with one oxvgen. Such a compound, predicted by the theory, 

 has been recently discovered, though not obtained in a separate 

 state as yet. Hence it follows, that the weight of sulphur which 

 enters into these combinations represents the proportional weight 

 of an atom of that substance. Then the combinations of oxygen 

 and sulphur will stand thus : 



100 sulphur + 50 oxygen hyposulphurous acid 

 100 sulphur + 100 oxygen sulphurous acid 

 100 sulphur + 150 oxygen sulphuric acid 



And if 100 represent an atom of sulphur, it is double the 

 weight of an atom of oxygen ; accordingly the weight of an atom 

 of sulphur is represented by 16 in reference to hydrogen, or by 

 li^when oxygen is taken as I . 



18. The combination of sulphur with hydrogen leads to the 



