to a pressure of 0.000076
millimeter, or 0.1 M. The negative electrode, A, is formed by coating
part of the outside of the bulb with silver, and it is in such a
position that the focus of rays falls upon the carbon wool. The
positive electrode, B, is an outer coating at the other end of the
tube. I pass the current, and those who are close may see the bright
sparks of carbon raised to incandescence by the impact of the
molecular stream.

You thus have seen that all the old "radiant matter" effects can be
produced in tubes containing no metallic electrodes to volatilize. It
may be suggested that the sides of the tube in contact with the
outside poles become electrodes in this case, and that particles of
the glass itself may be torn off and projected across, and so produce
the effects. This is a strong argument, which fortunately can be
tested by experiment. In the case of this tube (Fig. 23, P = 0.00068
millimeter, or 0.9 M), the bulb is made of lead glass phosphorescing
blue under molecular bombardment. Inside the bulb, completely covering
the part that would form the negative pole, A, I have placed a
substantial coat of yttria, so as to interpose a layer of this earth
between the glass and the inside of the tube. The negative and
positive poles are silver disks on the outside of the bulb, A being
the negative and B the positive poles. If, therefore, particles are
torn off and projected across the tube to cause phosphorescence, these
particles will not be particles of glass, but of yttria; and the spot
of phosphorescent light, C, on the opposite side of the bulb will not
be the dull blue of lead glass, but the golden yellow of yttria. You
see there is no such indication; the glass phosphoresces with its
usual blue glow, and there is no evidence that a single particle of
yttria is striking it.

[Illustration: Fig. 22.--Pressure = 0.000076 MM. = 0.1 M.]

[Illustration: Fig. 23.--Pressure = 0.00068 MM. = 0.9 M.]

Witnessing these effects I think you will agree I am justified in
adhering to my original theory, that the phenomena are caused by the
radiant matter of the residual gaseous molecules, and certainly not by
the torn-off particles of the negative electrode.

PHOSPHORESCENCE IN HIGH VACUA.

I have already pointed out that the molecular motions rendered visible
in a vacuum tube are not the motions of molecules under ordinary
conditions, but are compounded of these ordinary or kinetic motions
and the extra mo