Experiments with perforated electrodes on the nature of the discharge in gases at low pressures

In a paper on the influence of the nature of the cathode on the length of the Crookes' dark space some difficulties in the way of a satisfactory explanation of the mechanism of that phenomenon were indicated, which showed that it would be very advantageous to obtain, if possible, direct evidence as to how much of the total current passing through the discharge tube was brought up to the surface of the cathode by the positively charged ions falling upon it. With a view to investigating this and some kindred problems, a discharge tube was made of the form indicated in section in fig. 1. It consisted of a cylindrical glass shade, closed at the lower end by stout glass plate, the electrodes being flat zinc discs just filling the tube. Zinc was used instead of aluminium as hithertofore, as during the work with cathodes of different metals the former was found to give off very little gas and to sputter hardly at all, while the much greater ease with which it may be worked gives it a great advantages over the latter.