(6) _a._ Bulb No. 4 (see Plate XVIII. fig. 1) was placed between the poles of the excited magnet, and the current was passed and then stopped. The glow in that bulb faded away out of its order, and earlier than in ordinary cases (nearly as soon as No. 2). [Sidenote: Other bulbs tested in similar manner.] _b._ The same and other bulbs were tested in a similar manner. In all cases the bulb influenced by the magnet, when the current was stopped, was found perceptibly fainter in after-glow. [Sidenote: Effect of magnet upon the after-glow itself.] _c._ The tube was arranged with one of the bulbs between the poles of the unexcited magnet; the current was passed and stopped, and the after-glow obtained. The magnet being then quickly excited, the after-glow in the bulb, under its influence, faded out; and the bulb became transparent, perceptibly sooner than under ordinary circumstances. We tried this several times, with the same result in each case. [Sidenote: Mr. Thompson’s experiments on action of magnets upon liquid rings.] _Note._—In relation to these experiments, it may be mentioned that Mr. S. P. Thompson, of Bristol, is reported to have studied the action of magnetism upon rings of coloured liquid projected through water, and to have observed their retardation and partial destruction in passing through a powerful magnetic field. [Sidenote: Mr. Ladd’s explanation of some of the phenomena observed.] Mr. Ladd has suggested to me that some of the phenomena produced indicate a driving of the gas in the direction from the negative to the positive pole—a theory which is supported by the action of the magnet on the bulbs, if this be considered a repulsive one as regards the gas influenced. _Effect of Magnet on small Phosphorescent (powder) Tubes._ [Sidenote: Tubes containing phosphorescent powders described.] We examined six vacuum-tubes containing phosphorescent powders, which, upon exposure to sunlight and removal to the dark, or after passing of the electric current over them, continued to glow in the tubes after the exciting cause had ceased. They were of thin glass, and of equal calibre throughout. One was 6½ inches long and ⅝ inch in diameter, and had no label; the other five were 7½ inches long and ½ inch in diameter, and were labelled respectively:— Strontium vert, ” jaune, Calcium violet, ” orange, ” vert-bleuâtre. [Sidenote: Lighting-up of the tubes described. Effect of magnet on ⅝-diameter tube. Spectrum without magnet.]