1833.] Attraction and Repulsion. 449 
have no proof of different gases having the same number of particles 
in equal bulks. 
In the combination of gases, a comparison between their prime equi- 
valents, their proportions by volume, and the resulting bulks of the 
compounds, would lead to the conclusion that the number of particles 
in a given bulk differed materially in different gases. Thus, if it be 
assumed that in oxygen and nitrogen the number of atoms in a given 
bulk of each is equal, since one volume of the former combines with 
one of the latter to form the nitric oxyd gas, it would follow, that an 
atom of each unite to form each particle of the compound gas. _ If, 
then, in the latter, it be assumed, that in a given bulk the same number 
of compound particles exist as of simple ones in either of the former, it 
is clear that the two volumes ought in combining to condense into 
one volume, since two atoms form one compound particle. But expe- 
rience shews that no condensation takes place. Therefore, whatever 
number of simple atoms have combined to. form a compound particle, 
in the same proportion must the number of the latter in a given space 
have decreased. 
Many other combinations of gases would prove equally hostile ta 
the supposition, that all gases are at the same temperature and pres- 
sure equally dense. Hence, though equal rises of temperature may in- 
crease the bulks of different gases equally, the separation of the parti- 
cles may differ in all. And further, the capacities of gases for heat dif- 
fer materially. If equal bulks of hydrogen and olefint gases be taken, 
since their relative capacities for heat are as 1 to 1.7 nearly, we 
shall have these numbers representing the relative quantity of heat. by 
each degree of temperature. It would require 1.7 of heat to expand 
an equal bulk of hydrogen. Since the pressure on each is equal 
and increases equally, whence does this arise? We are compelled, I 
think, to conclude that atmospheric pressure is not the sole force op- 
posing expansion, but that it is aided also by an attraction subsisting 
between particles in the gaseous state, more powerful in olefint gas 
than in hydrogen, whence to effect an equal expansion more heat is re- 
quired in the former than in the latter. J 
If then any inference can be drawn from the equable expansion by 
heat of different gases, it is this, that in every gas an attraction sub- 
sists between the atoms ; but in some gases, as mighthave been expect- 
ed, more powerful than in others. 
By the above elaborate inquiry, I trust I have shewn that the facts 
usually brought forward as evidence of the limited distance to which 
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