524 On the two great powers, [Ocr, 
To this, however, I may state an objection of another nature, and 
no less powerful. If these two powers are so equal at every distance, 
as to neutralize each other, what must be the effect of the smallest 
addition or abstraction of heat ? 
In the one case, repulsion becoming the stronger force, the gases 
must be totally separated. In the other, the attraction predominating 
will bring the atoms into contact, much more then into intimate com- 
bination. 
2. Secondly, That between mixed gases the repulsive force is 
stronger than the attraction. Under this head may perhaps be placed 
the last modification of Mr. Dauton’s theory. He admits of gases 
being mutually repellent, but lays down the following maxim on which 
he explains the mixture. ‘‘ That every species of pure elastic fluid, 
has it particles globular and all of a size. But that no two species 
agree in the size of their particles, the pressure and temperature being 
the same*.” 
Hence Mr. Datron argued, that in a pure gas the atoms being all 
of a size can remain at rest, as the pressure must be equal through- 
out. But when a gas of larger atoms is placed on the former, that 
the pressure of their atoms owing to a difference of size will be irre- 
gular and unequal ; and that therefore an intestine motion must ensue, 
until, the gases having mixed, each can rest on the same base. 
Even if the atoms of bodies endowed with their atmospheres of heat 
were spherical, it is very questionable whether the above doctrine, 
though evincing much ingenuity, be really applicable. 
It is difficult to say what would be the effect of spheres of different 
sizes pressing on each other. But the atmospheres of heat round atoms 
are highly elastic, and hence do not press on each other by single 
points only, as inelastic spheres would ; but must assume some form 
requisite for general and regular contact ; without mixing. Thus if a 
long hollow cylinder placed perpendicularly, and closed at the upper 
end, have the air of a few inches from the top heated ; the atoms of 
- the heated air being enlarged (it might be greatly), and according 
to Mr. Datton’s theory, pressing unequally on those below, a mixture 
ought to take place. The heated air ought to descend and diffuse it- 
self completely among the cold air, There is little doubt, however, 
that no sych occurrence would take place ; the heated air would con- 
tinue above. But let the cylinder be inverted, and the heated air will rise 
tion of water, and its lessening the density of the atmosphere. The objections 
stated under that head still remain. 
* New System of Chemical Philosophy, p. 189. 
