= 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 motion due to the electrical impetus.
Experiments show that in such tubes a few molecules may traverse more
than a hundred times the _mean_ free path, with a correspondingly
increased velocity, until they are arrested by collisions. Indeed, the
molecular free path may vary in one and the same tube, and at one and
the same degree of exhaustion.
Very many bodies, such as ruby, diamond, emerald, alumina, yttria,
samaria, and a large class of earthy oxides and sulphides,
phosphoresce in vacuum tubes when placed in the path of the stream of
electrified molecules proceeding from the negative pole. The
composition of the gaseous residue present does not affect
phosphorescence; thus, the earth yttria phosphoresces well in the
residual vacua of atmospherical air, of oxygen, nitrogen, carbonic
anhydride, hydrogen, iodine, sulphur and mercury.
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