The theory of expansion is of easy comprehension; it consists in
previous de-electrisation, succeeded by influent medium of space,
which, by acting with centrifugal pressure, produces the phenomenon of
expansion. The general pressure is the expanding cause, by reason of
the portion of medium of space within all bodies being continuous with
the medium of pressure in general space.
A bar of iron placed within the medium of fire suffers
de-electrisation; then acquires medium of space, by which the bar is
expanded. When taken from the fire, it acquires electric matter similar
to that of which it had suffered loss, which displaces the expanding
medium, and now becomes contracted by external pressure. The olden
philosophy has no contracting cause, the imputed attraction having
been destroyed by the imputed heat of the fire, as the same philosophy
states of the imputed attraction of magnets being destroyed by the heat
of fire, which leaves the bar to contract itself.
A piece of lead on the fire becomes de-electrised and expanded. The
portion of medium of space it has acquired separates the atoms of
the lead by which the state of solidity is subverted; it remains as
one of the constituents of the lead, and is as a menstruum to the
metal, and the atoms of the metal may be said to swim in it as the
globules of blood in the serum. Further de-electrisation and additional
increments of medium of space are productive of complete dispersion of
the atoms of the metal, and of a kind of efflorescent result, which
is a subsequent formation. The air in a corked bottle before the
fire loses electric matter to the medium of fire; and by the medium
of space which enters the vacated interstices, the cork is exploded.
In the partially exhausted air-pump receiver, that decrease in the
quantity of air should increase the expansive power of the remainder,
and that the atoms should fly asunder with exploding force, is most
unreasonable and impossible. The physical fact is, the more the air
is reduced, the greater is the quantity of influent medium of space,
consequently of expanding and exploding force. In the condensing of
air, as is the expression, by the piston of the syringe, the quantity
is reduced from being forced out through the pores of the syringe; and
pressure on the bottom of the piston springs it up when the depressing
power is removed. Under the general pressure the atoms of air must
be in contact; and the volume being reduced, implies reduction of
quantity: hard unalterable atoms are incompressible beyond contact;
and as to their being elastic, it is physically impossible; medium
of space being forced out and re-entering, is what makes the air be
considered elastic. Let the syringe be worked under water, and the
matter displaced appears escaping as air-bubbles, and as air-beads on
the outside of the syringe.