y means of the particles, or atoms of air that exist
between the two surfaces of the balloons, and that transmission would
take the form of a wave propagated from particle to particle, so that we
might put dots on the right side of _A_ to represent the atoms of air
which transmit the wave from _A_ to _B_.

But the vibration which takes place in the surface of the envelope of
the outer balloon is _across_ this line of propagation, because as the
wave proceeds from _A_ to _B_, the elastic envelope expands and
stretches always _across_ the line of propagation--that is, it stretches
up and down, left and right, as it is expanded outwards, so that the
vibration or oscillation of the particles always takes place in the
surface of the elastic envelope across the line of propagation. Let us
therefore apply the result of this simple experiment to our solar system
and the Aether, and see if it can be made to explain the transverse
vibration of light. Let _A_ represent the sun (Fig. 7) and _B_ an
aetherial elastic envelope surrounding the sun. In this case we dispense
with the bulb _C_, as the sun possesses within itself the power to
generate heat, and so to produce the required expansion of the elastic
aetherial envelopes _B_, _G_, _H_, etc.

[Illustration: Fig: 7.]

Instead, however, of having air particles between _A_ and _B_, we will
put in their place our aetherial atoms which we have conceived according
to Art. 44. These surround the sun, represented by _A_, forming elastic
spherical shells or envelopes. As the sun radiates its heat into space,
it urges the aetherial atoms against each other, with the result that
they transmit the energy from atom to atom, or particle to particle,
till they come to the elastic aetherial envelopes of _H_, _G_, _B_.

The effect on _B_, or on any other aetherial envelope, is to expand it
outwardly, and thus set the atoms of which it is composed into
vibration. The wave, which is now an aetherial wave travelling with a
velocity of 186,000 miles per second, may be represented by the line _D_
_E_. But while it is travelling from _D_ to _E_ the same energy is being
radiated out in all directions, so that a wave reaches the whole surface
of the elastic envelope _B_ at the same time, with the result that the
whole of the shell or envelope is set in vibration as it expands
outwardly.

Thus the vibration is always in the wave front, and the wave front is
always coincident with the surface of one o