pressure of light is proportionate
to the amount of incident energy, and is independent of the colour of
light; 3rd, that the pressure of light corresponds with the forces of
radiation as calculated by Maxwell.

About the same time, Nichols and Hull of America were engaged upon
experiments relating to the pressure of light waves, and their results
were published in the November _Physical Review_, 1901. Thus, from two
separate and independent sources, Maxwell's equations as to the pressure
which light waves exert upon any body on which they fall received
definite experimental confirmation.

The repulsive power of the light waves receives further confirmation from
that theory known as the electro-magnetic theory, which supposes light to
be nothing more or less than an electro-magnetic phenomenon; that is to
say, it is directly or indirectly due to the action of electric currents.

As already indicated, Lorentz was of the opinion that the light waves
were themselves electric currents, and whether this is the actual fact
or not, certainly it is true that the electro-magnetic theory of light
is no mere fable or myth, but that it ranks as one of the most advanced
and correct hypotheses in regard to light that has ever been given to
the world. According to that theory, which we shall look at
subsequently, we find that the aetherial medium is not only the medium
for the light waves, but that it is also the medium which conveys and
carries the electric currents through space, and even through all
matter. Further, from that theory we shall have good reasons for
assuming that the aetherial light waves are either themselves electric
currents, or closely identified with them, in the same way that the
light waves are identified with heat waves. If these facts should be
found to hold good relative to the identity of aetherial light waves and
the aetherial electric waves, then it can very readily be seen that such
a hypothesis gives added weight to the repulsive power of light. One of
the very commonest facts regarding electricity and its currents is, that
wherever we get electricity, we not only get attraction, but there is
always associated with that attractive force a repulsive force, which is
equal in amount to the attractive force. So that if, wherever we get
electric currents, we find associated with those currents a repulsive
force, then, in view of the electro-magnetic theory of light, it should
also follow that on that hypot