Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1866-05-11
All Things i'm Motion.

In imagining the ultimate composition Of
solid body, we have to reconcile two ap-
parently contradictory conditions. 1t is an
assembage of atoms which do not touch
each other--for we are obliged to admit in
termolecular spaccs-and yet those atoms
are held together in clusters by so strong a
force OF cohesion as to give the whole the
qualities of solid. This would be the case
even with solid undergoing no change Of
size or internal constitution, But solids do
change, under pressure, impact, heat, and
cold. Their constituent atoms are, conse-
qucntly, not at rest. Mr.. Grove tells us :
"Of absolute rest nature gives us no evil
dcnce. All matter rs far as we can ascer-
tain, is ever in movement, not merely in
masses, as with the planetary spheres, but
also molecularly, or throughout its most in
innate structure. Thus every alteration of
temperature produces molecular change
throughout the whole substance heated or
cooled. Slow chemical or electrical actions,
actions of light or invisible radient forces,
are always at play so that, as fact, we
cannot predicate Of any portion Of matter,
that it is absolutely at rest"
The atoms, therefore, of which solid bod
les consist are supposed to vibrate, to oscil-
late or better, to revolve, like the planets,
in more or less eccentric orbits. Suppose a
I
gnats dancing in the sunshine. Each gnat
or atom dances up and down ut certain
distance from each other gnat, within Civ
en- limited space. The path Of the dance is
not mere straight line, but vertical oval
"a true orbit Suppose then that in conse-
quence of greater sun heat, the gnats become
more active. and extend each its respective
sweep of flight. The swarm, or solid body
as whole expands. If from chill or the
shadow of a cloud, the insects individual
range is less extensive, the crowd of gnats is
necessarily denscr and the swarm, in its in
tegrity, contracts.
Tyndall takes for his Illustration a bullet
revolving at the end of "A spiral spring. He
had spoken of the vibration of the molecules
of Il solid as causing its expansion, but he re-
marks that. by some the molecules have
been thought to revolve round each other
the communication of heat, by augmenting
their centrifugal force was supposed to push
them more widely asunder. SO he twirls
the weight mt the end Of the spring in the
open air. 1t tends to fly away the spring
stretches to n certain extent. and as the speed
of revolution is augmented, the spring
stretches still more. the distance between the
hand and the weight being thus increased
The spring rudely figures the force of CO.
hesion, while the ball represents an atom
under the influence of heat
The intellect, he truly says, knows no diff
ference between great and small. 1t is just
rs easy, as an intellectual act, to picture q
vibrating or revolving atom rs to picture &
vibrating or revolving cannon ball. These
motions, however, are executed within lin
its too minute and the moving particles are
too small. to be visible. Here the imagina.
ton must help us. In the case of solid bod
les, you must conceive q power of vibration
within certain limits, to be possessed by the
molecules. You must suppose them oscilla-
ting to and fro the greatet amount of heat
we impart to the body, the more rapid viii
he the molecular vibration, and the wider
the amplitude of atomic oscillation.-Al
The Year Round.