530 On the two great powers, [Ocr. 
Distances. 1 2 3 4 5 6 7 
Pres. of the air, 1 4 9 16 25 36 49 
Attraction, 1024. 256 113.7 64 40.9 28.4, 20.8 
Ay F A By * 
Repulsion, 5120 640 189.6 80 40.9. 23:7 . Y¥4:8* 
Here it is manifest, that both the mutual attraction of the atoms, 
and the pressure of the air, are tending to compress thie fluid. 
Tf the former force only operated, the atoms would be at distance 5 
from. each other; as there the attraction and repulsion would’balance 
each other, and constitute a stable equilibrium. But since the latter 
force (pressure), operates on the liquid, the atoms are brought nearer 
to each other, to distance 4 (e. g) where the attraction and pressure, 
amounting together, to aforce (16 +64 =)80, are balanced by the repul- 
sive force, which at that distance is also 80. The point of stable equi- 
librium is thus removed to a smaller distance, where, as:long as the 
same forces operate on the atoms, they can neither approach nor recede 
ofthemselves. Again as, in a liquid, theatoms are pressed within the dis- 
tance, at-which the attraction alone balances.the repulsion, by a force 
(the pressure of the air), the effect of which is merely.to keep the 
liquid within a certain bulk, it is manifest, that. this.erternal force 
does not operate towards keeping any two atoms.in particular near to 
each other. Hence the atoms may move on each other, as long as 
others supply their place. And thus the peculiar character.of the: 
liquid state may be explained. 
The remarkable property of a liquid, of collecting itself into drops 
under certain circumstances, may also be readily explained by this law. 
The pressure of the air can. have no more effect in forming. liquids 
into spherical drops, than into drops of any other form,. The only. 
force, which can effect this, is the attraction of the atoms, which, as 
in the diagram, though weaker than the repulsion between. the neigh- 
bouring atoms A and B, must become the more powerful force. be- 
tween any, but neighbouring atoms; and being the more powerful 
of temperature. Atmospheric pressure can only act on this vapor (whose atoms 
are perfectly intermingled with its own) so far as it is endeavouring to expand the 
air, and can only increase the density of the vapor, until the elasticity of the at- 
mosphere itself prevents its own atoms from approaching nearer to each other, or, 
in other words, until the vapor is of the same density as the natural density of the 
air; the force therefore, which in this case reduces the vapor into a liguid, must 
be an effective attraction, and in part the gravity of the vapor. 
* The first of these forces, the pressure of the air, varies as the square of the 
distance of the atoms. The second, the attraction, varies inversely as the square 
of their distance. The third, the repulsion, varies in any higher inverse ratio of 
the distance, e. g. inversely as the cube of the distance. 
