material of the poles.

Puluj declares that the phenomena I have described in high vacua are
produced by his irregularly shaped lumps of radiant electrode matter.
My contention is that they are produced by radiant matter of the
residual molecules of gas.

Were it not that in this case we can turn to experimental evidence, I
would not mention the subject to you. On such an occasion as this
controversial matter must have no place; therefore I content myself at
present by showing a few novel experiments which demonstratively prove
my case.

Let me first deal with the radiant electrode hypothesis. Some metals,
it is well known, such as silver, gold or platinum, when used for the
negative electrode in a vacuum tube, volatilize more or less rapidly,
coating any object in their neighborhood with a very even film. On
this depends the well known method of electrically preparing small
mirrors, etc. Aluminum, however, seems exempt from this volatility.
Hence, and for other reasons, it is generally used for electrodes.

If, then, the phenomena in a high vacuum are due to the "electrode
matter," the more volatile the metal used, the greater should be the
effect.[6]

[Footnote 6: In a valuable paper read before the Royal Society,
November 20, 1890, by Professors Liveing and Dewar, on finely divided
metallic dust thrown off the surface of various electrodes, in vacuum
tubes, they find not only that dust, however fine, suspended in a gas
will not act like gaseous matter in becoming luminous with its