IX. On stratified discharges. VII. Multiple radiations from the negative terminal

In our memoirs “On the Sensitive State of Vacuum Discharges” we have often alluded to, and even insisted on, the importance of the remarkable dissymmetry which manifests itself in electrical discharges in gases at low pressures. As the pressure is lowered this dissymmetry becomes more and more marked; the striæ themselves become individually unsymmetrical, and recede one by one into the positive terminal; the features which are associated with the negative increase in importance, until at last they occupy almost the entire area of the tube. The researches of De La Rue, Crookes, Goldstein, and others, have intended to increase the interest which attaches to the action which takes place at the negative terminal. And it is with a view of adding one more contribution to the interpretation of the phenomena of the negative discharge and the analysis of its nature andmodus operandi that the present experiments are described. On examining the image of a negative terminal as traced out in tubes of great exhaustion, by the phosphorescence due to Crookes’ radiations, we have often noticed that the image was not a simple figure, but that more than one outline of the contour of the terminal might be traced. From the fact of the double contour having been first remarked, where the terminal was of a conical form, it was at first supposed that the second image might be due to internal reflexion, or to some property appertaining to the edge of the cone. But this supposition led to no satisfactory explanation of the phenomenon.