1833.] Attraction and Repulsion. 457 
-Tn short, as all powers inherent in atoms must be permanent, and 
as a permanent repulsion cannot alone account for densities and states, 
which are not constant, the power opposing attraction cannot be solely 
a power inherent in atoms. 
Secondly. Whether the opponent force to the attraction of atoms 
depends on a power exerted by them, aided by the power, heat. 
In a modern treatise on attraction* and repulsion, it is thus assert- 
ed :—‘‘ The states of elastic fluidity, solidity, and liquidity, in all of 
which the greater number of simple bodies are capable of being exhi- 
bited, at different temperatures, are not uncommonly conceived to de- 
pend on the different actions of heat only, giving a repulsive force to 
the particles of gases, and simply detaching those of liquids from that 
cohesion with the neighbouring atoms which is supposed to constitute 
solidity.”” And he adds, “ but these ideas, however universal, may be 
easily shewn to be totally erroneous : and it will readily be found, that 
the immediate effect of heat alone is by no means adequate to the ex- 
planation of either of the changes of form in question.” ‘‘ There can 
never be rest, without an equilibrium of force, and if two particles of 
matter attract each other, and yet remain without motion, it must be 
because there exists also a repulsive force, equal, at the given distance, 
to the attractive force.” 
To this I answer.—It is undoubtedly true, that, to enable the parti- 
cles of a body to be at rest, the opponent forces, operating on them, 
must be in equilibrio. And the remark, just quoted, might properly 
be objected to those writers who have treated of the force of attrac- 
tion between the particles of solids, as being greater than the repul- 
sion. But, since the question is, whether or not heat be the repulsive 
power which keeps bodies in the gaseous, the liquid, and the solid 
state, this remark cannot be considered as a proof on either side, since 
it has no reference to this question. 
Admitting heat as the sole source of repulsion between atoms, its 
force may easily, nay must be considered, as equal to that of the at- 
traction, whenever particles are at rest. The opponent powers must 
be in equilibrio, whether heat be the source of repulsion, or not. 
In the same treatise also, attraction and repulsion, it would appear, are 
considered as being both exerted between atoms, at all distances within 
a certain limit. In the first place, it cannot be admitted as possible, 
that at the same distance, the same particles should at once attract and 
repel each other. But even supposing it possible ;—if this repulsion 
* EncycLopapi1a Britannica, Supplement, Art. Cohesion. 
2N 
