ect the sense of
sight.

Heat, then, is due to some motion in the universal aetherial medium,
that not only fills all space, but also forms an atmosphere around every
atom or particle of matter that exists in the universe, and that motion
is generally known as a vibratory or backward and forward motion.

Heat, then, may be said to be due to the vibrations of the Aether that
surrounds all atoms and molecules, and of which those very atoms are
composed, that is if we accept the aetherial constitution of all matter.
So that, whenever a body, whether it be an atom or a molecule, or a
planet or sun or star, is heated in any way whatever, such bodies excite
waves in the surrounding Aether, and these waves travel through the
Aether towards us from the heated body with the velocity of light. When
these waves fall upon any other body, they become more or less absorbed
by the body on which they fall, and cause corresponding vibratory
motions in the same, which give rise to the phenomenon of heat in that
particular body.

It has to be remembered that nothing definite is actually known as to
the character of this vibratory motion. It is called a vibratory motion
because it possesses a periodic vibratory movement, but as to its exact
character, that has not yet been discovered. I hope, however, to
indicate what the motion is that produces heat before the completion of
this work.

ART. 61. _Heat and Matter._--If it be true that heat is due to the
vibrations of the aetherial medium, the question now arises, as to how a
body may become heated, and by so doing be transformed into the three
stages in which matter is found. We have already seen (Art. 36), that
matter may be found in three forms, viz. solid, liquid, and gaseous, and
that all these different forms of matter are composed of minute parts
called atoms. In the case of the solid, the atoms are held closely
together by some strong attractive power, termed cohesion; in the case
of the liquid, the atoms have a greater freedom; while in the gaseous
form they have a greater freedom of movement than when in either the
liquid or the solid state. According to Young's Fourth Hypothesis (Art.
45), we find that all matter, and therefore all atoms have an attraction
for the Aether, by means of which it is accumulated within their
substance, and for a small distance around them in a state of greater
density, and therefore of greater elasticity. In other words, as Aether
is gravitative