The experiment is too lengthy for me to repeat it here, so I shall not
attempt it; but I have on the table the results for examination.

The identity of action of silver and aluminum in the first case, and
the non-projection of silver in this second instance, are in
themselves sufficient to condemn Dr. Puluj's hypotheses, since they
prove that phosphorescence is independent of the material of the
negative electrode. In front of me is a set of tubes that to my mind
puts the matter wholly beyond doubt. The tubes contain no inside
electrodes with the residual gaseous molecules; and with them I will
proceed to give some of the most striking radiant-matter experiments
without any inner metallic poles at all.

[Illustration: FIG. 16.--PRESSURE = 0.00068 MM. = 0.9 M.]

In all these tubes the electrodes, which are of silver, are on the
outside, the current acting through the body of the glass. The first
tube contains gas only slightly rarefied and at the stratification
stage. It is simply a closed glass cylinder, with a coat of silver
deposited outside at each end, and exhausted to a pressure of 2
millimeters. The outline of the tube is shown in Fig. 17. I pass a
current, and, as you see, the stratifications, though faint, are
perfectly formed.

[Illustration: FIG. 17.--PRESSURE = 2 MM.]

The next tube, seen in outline in Fig. 18, shows the dark space. Like
the first it is a closed cylinder of glass, with a central indentation
forming a kind of hanging pocket and almost dividing the tube into two