the repulsive power of heat gave rise to the tails of comets, is
correct. Then again it has been suggested that the repulsive power is
produced by the pressure of the light waves. Professor Lebedew suggested
this after he had experimentally proved that light waves did possess a
repulsive power (_Annalen der Physik_, November 1901). It can easily be
seen, as pointed out in Art. 70, that, inasmuch as light is due to the
vibrations of the Aether, they too possess this repulsive power, and
therefore Professor Lebedew's suggestion as to the nature of the
repulsive power is correct, as the real centrifugal force is really due
to an aetherial pressure.

Whether, therefore, we consider it from the standpoint of heat, or light
or electricity, it ultimately resolves itself into the same aetherial
medium which is at once the common source of all these forces. Again, it
has been suggested that the repulsive power is electrical or
electro-magnetic, and this view is receiving more support than either of
the others from modern scientists.

Herschel suggested that the repulsive power was electrical, while
Bredichin has worked out a very careful theory as to the effect of
electrical repulsion upon different elements that are found in the
comets' tails, with a view to explain the different shapes of the tails.
But whether the force is looked at from the standpoint of heat, light or
electricity, it ultimately resolves itself into the motions of the
Aether, which gives rise by its different vibrations and motions to all
the three forms of energy referred to.

When we also take into account the fact that Aether is gravitative, and
therefore denser nearer to the sun than further away, and that it is
also rotating round the central body the sun (Art. 91), then we have at
once every condition necessary to explain all the various kinds of
cometary tails, and also for the remarkable fact that the tail is always
turned away from the sun, which is simply due to the effect of the
rotating Aether with its outflowing electro-magnetic waves upon the
gaseous matter of the comet. Thus from the phenomena of comets' tails,
we have again arrived at the conclusion of the existence of that
centrifugal force, whose origin and continuity are to be found in the
electro-magnetic Aether which surrounds the sun, and which by its
electro-magnetic waves gives rise to pressure on all bodies upon which
they fall.

ART. 116. _Formation of Tails._--With the concep