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