Bell-shaped receiver described. Discharge described.
(2) A bell-shaped receiver, with terminals inserted at the sides and one also at the top, was next used (see Plate XVIII. fig. 9). When the side terminals were employed, the effect was much the same as in the last case. When the top terminal was used for one wire (the other wire being connected with the pump-plate) a single stream of bright rosy light ran from the upper terminal to the plate. First striking the central part of the plate, the stream then glided towards one of the lateral terminals, and so to the edge of the receiver. After partly discharging itself by contact with the terminal, the stream as rapidly retreated to the centre of the plate again—this effect being from time to time repeated while the current was passing. The current being reversed, a number of bright, but weaker and more diffused, streams of light had the appearance of shooting from the upper electrode, and of striking upon the plate below; with a tendency to fly off from where they struck, in a similar manner to the single stream before described. Where each stream touched the plate a brilliant point of light appeared, and a strong pattering noise was heard in the receiver.
Bell-shaped receiver without electrodes. Induction discharge described.
(3) Another bell-shaped receiver of similar shape was used. This had no electrodes forming a direct communication with the interior; but, in lieu of these, two wafers of thin sheet brass were cemented, one inside and one outside the glass, opposite to one another. On connexion being made with the outside wafer, the effects produced by induction were similar to, and very nearly as strong as, those in the cases where direct communication with the interior of the receiver was made.
Long large tube exhausted and illuminated. Spiral form of discharge.
(4) A large tube, 24 inches long and 2 inches in diameter, with ball and point electrodes respectively, was exhausted, and the current passed through it. The effects were similar in most respects to those produced in the globular and bell receivers, but the streams of light assumed a distinctly spiral form in their passage (see Plate XVIII. fig. 5). This tube when placed between the poles of the magnet showed no effect, except a slight condensation of the streams of light towards the sides of the glass.
Globular receiver again used.
(5) The globular receiver first described was again used (the Tate pump having been cleaned and working easier).
Phosphorescent after-glow succeeding the spark.
(a) When exhaustion was as good as it could be got, the spark struck across in a single, slightly expanded, stream of rosy light, having a tendency to curve upwards (see Plate XVIII. fig. 6). The electrodes had but little glow round them, only just enough to distinguish the poles apart. When the flow of the stream was interrupted by breaking contact with one terminal, so that sparks passed in succession, we thought we detected a faint blue phosphorescent after-glow succeeding each spark.