1820.] the Atomic Theory. 201 



The fact, that in every inorganic combination one of the elements 

 enters as miity, is founded on numberless experiments, and is a 

 deduction from the analytical researches of some of the ablest 

 chemists, particularly of Berzelius, who veritied it in all the inor- 

 ganic bodies which he analyzed. 



We have seen how strikingly this law is exemplified in the 

 union of oxygen and hydrogen gases, and that the proportion in 

 which they combine is definite. 



12. Whereas the atoms of one kind of gas repel each other 

 among themselves, and those of different gases attract each 

 other, it follows that when they are mixed equably, as is the 

 case when 2 measures of hydrogen and 1 of oxygen gas are putinto 

 a tube and fired by electricity, they will most readily unite atom 

 to atom. Until very lately there was no combination of oxygen 

 and hydrogen known, but that in which they exist in water; it 

 was, therefore, concluded that this was the proportion in which 

 they unite most readily, and with the greatest force. Of late, a 

 new compound of oxygen and hydrogen has been formed by 

 Thenard, consisting of one atom of hydrogen with luore atoms 

 of oxygen. This discovery tends fully to confirm the former 

 opinion, viz. that the first formed combination is one of atom to 

 atom. 



13. It also follows from a consideration of the volmnes in 

 which oxygen and hydrogen gases combine, that a given bulk 

 of hydrogen contains only one half the number of atoms that 

 exist in the same bulk of oxygen gas. 



Here it may not be superfluous to remind the student that the 

 density of gases difters like that of other bodies, and that under 

 the same volume they contain unequal quantities of matter. A 

 remarkable example of the fact is afforded by ammoniacal gas, 

 which can be expanded by repeated shocks of electricity to 

 almost twice its original bulk. Consequently, in this new state 

 its atoms are nearly twice as distant as they were at first, and 

 any given measure of it contains now but about half the number 

 of atoms which the same measure contained before. 



14. Out of the consideration of this difference naturally arises 

 that of the cause which keeps asunder the atoms of gases and 

 of all other bodies ; for, however strong we may deem their affi- 

 nity, they can never touch. On the supposition that two atoms 

 were in actual contact, their attraction for each other w(»uld not 

 only be as great as possible, but as great as the attraction of any 

 other body, for either of them, could possibly be ; because, by 

 the supposition, they cannot be nearer. Consequently since 

 bodies chemically combined can be separated, they are not in 

 actual contact, but their distance from one another may vary in 

 different cases, and then the force of affinity will vary with the 

 distance. All bodies are diminished in bulk by cold; it brings 

 their particles nearer together, which would be impossible unless 

 they had been at some distance before they were cooled. This 



