vibrations in the air; motion, or the energy which it implies, is the
life of the universe.

Physics proves to us the impossibility of perpetual motion among
visible, tangible bodies, at the same time that it reveals to us a world
where perpetual motion is the rule--the world of molecules and atoms. In
the world of gross matter, or of ponderable bodies, perpetual motion is
impossible because here it takes energy, or its equivalent, to beget
energy. Friction very soon turns the kinetic energy of motion into the
potential energy of heat, which quickly disappears in that great sea of
energy, the low uniform temperature of the earth. But when we reach the
interior world of matter, the world of molecules, atoms, and electrons,
we have reached a world where perpetual motion _is_ the rule; we have
reached the fountain-head of energy, and the motion of one body is not
at the expense of the motion of some other body, but is a part of the
spontaneous struggling and jostling and vibration that go on forever in
all the matter of the universe. What is called the Brunonian movement
(first discovered by the botanist Robert Brown in 1827) is within reach
of the eye armed with a high-power microscope. Look into any liquid that
holds in suspension very small particles of solid matter, such as dust
particles in the air, or the granules of ordinary water-color paints
dissolved in water: not a single one of the particles is at rest; they
are all mysteriously agitated; they jump hither and thither; it is a
wild chaotic whirl and dance of minute particles. Brown at first thought
they were alive, but they were only non-living particles dancing to the
same tune which probably sets suns and systems whirling in the heavens.
Ramsay says that tobacco smoke confined in the small flat chamber formed
in the slide of a microscope, shows this movement, in appearance like
the flight of minute butterflies. The Brunonian movement is now believed
to be due to the bombardment of the particles by the molecules of the
liquid or gas in which they are suspended. The smaller the particles,
the livelier they are. These particles themselves are made up of a vast
number of molecules, among which the same movement or agitation, much
more intense, is supposed to be taking place; the atoms which compose
the molecules are dancing and frisking about like gnats in the air, and
the electrons inside the atoms are still more rapidly changing places.

We meet with the same