From the negative (straight electrode) pole sprang a dense and compact arc of violet light, in the direction of the magnetic curves, which terminated at the upper circumference of the tube, but which, if prolonged, would have followed the curves to the opposite pole. The stream from the positive pole was very considerably brightened, as in the other experiments, but did not appear in the form of rings or waves. It assumed that of a bright steady continuous glow, which formed round the tube a not perfectly continuous, but distinct and well-marked, spiral. This form of discharge seems connected with the peculiar contour of the rings mentioned in experiment 2. One might, indeed, conjecture the spiral-shaped glow to be a ring of light extended or drawn out towards the negative pole. [Sidenote: Effects like those obtained by Gassiot.] Experiment No. 2 seems in result very like that of Gassiot’s with his grand battery and the Royal Institution magnet, the effects (though of course upon a smaller scale) being similar to those obtained by him. _Effect of Magnet on Plücker Tube (Tin Chloride)._ [Sidenote: Plücker tube (tin chloride). Lighting-up described.] A large Plücker tube was examined, which had a bulb attached at each end, communicating with the central portion by a narrow neck or constriction. On connexion with the small coil, a narrow stream of pale diffused cobalt-blue light ran along the whole tube, from point to point of the electrodes, the positive wire at the same time glowing with an aura of amber-yellow light. (See Plate XVII. fig. 3, where the narrow stream of light is shown by dotted lines.) At the two necks or constrictions the stream of light was perceptibly brightened. [Sidenote: Effects of magnet upon the stream.] When the magnet was connected, the stream in the positive bulb was not much changed, but only slightly bent. In the central partition of the tube and in the negative bulb, the stream of light was broken and split into a number of smaller streams, and at the same time bent or forced against the sides of the tube. (See Plate XVII. fig. 3.) [Sidenote: Peculiar noise within the tube.] In the central partition, the blue streamlets were accompanied by a number of spark-like threads of golden light, which shone out among them as the whole vibrated against the side of the tube; at the same time a peculiar pattering, as of a miniature hail-storm within the tube, made it ring with a slightly metallic tinkle. The direction of the bending or deflection of the stream was at right angles to the axis of the poles of the magnet, and changed from side to side of the tube as the direction of the current from the coil was varied. [Sidenote: Spectrum described. Without magnet. With the magnet excited.]