From the fact that the vacuum became higher and higher by the means stated, he was very much inclined to believe that there was an expulsion of material particles through the walls of the bulb. When these particles which were passing with very great velocities struck the sensitive photographic plate they should produce chemical action. He referred to the great velocity of projected particles within a discharge tube, pages 46 and 47, and to Lord Kelvin’s estimate upon the same, and reasoned that with very high potentials, the speed might be 100 km per second. The phenomenon indicated, he said, that the particles were projected through the wall of the tube and he entered into an elaborate discussion on this point. He referred to his own experiment of causing the rays from an electrode in the open air to pass directly through a thick glass plate. § 13. He performed an experiment also of producing a blackening upon a photographic plate apparently by the projected particles, an electrical screen being employed to prevent the formation of sparks. § 35. which as well known will cause chemical action upon the plate. No stronger proof as to the expulsion of material particles could be desired than an operation in which the eyes can see for themselves that such an action must have taken place. Usually he was troubled by the streamers (cathode rays) from the electrode suddenly breaking the glass of the discharge tube. This occurred when the spot struck was at or near the point where the same was sealed from the pump. He arranged a tube in which the streamers did not strike the sealing point, but rather the side of the tube. It was extraordinary that a visible but fine hole was made through the wall of the tube, and especially that no air rushed into the vacuum. On the other hand, the pressure of the air was overcome by something rushing out of the tube through the hole. The glass around the hole was not very hot, although if care were not taken, it would become much hotter, and soften and bulge out, also indicating a pressure within, § 27. greater than the atmospheric pressure. He maintained the punctured tube in this condition for some time and the rarefaction continued to increase. As to the appearances, the streamers were not only visible within the tube, but could be seen passing through the hole, but as the vacuum became higher and higher, the streamers became less and less bright. At a little higher degree of vacuum, the streamers were still visible at the heated spot, but finally disappeared.