ON ELECTRICAL DISCHARGES THROUGH RAREFIED GASES. 
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glow did not assume the form of an anchor ring, but of a surface of revolution, the 
section of which through its axis was bean-shaped, as represented in Plate 18, fig. 27. 
The glow as a whole had the ordinary whitish appearance, but the blunt protuberance 
or boss, opposite to the centre of the ring (marked R in the figure), where we should 
naturally assume any action that might be going on in the glow to be most intense, 
was deeper in tone and was precisely like a stria in appearance, both as regarded 
colour and shape, save that it was at its edges continuous with the negative glow. 
And when a certain change was made in the current by an alteration of some of the 
circumstances of the external circuit, a small conical stria appeared within the negative 
glow, just in front of the boss above spoken of, and quite separated from it, the two 
resembling in all respects (save in their position relative to the negative glow) two 
small striae separated by the usual dark space, the dimensions of the latter being, like 
those of the two striae, very small. 
Again, Plate 18, fig. 28, represents the variations of the negative glow, and its 
transition into a complete striated form, under the influence of a perforated disk 
terminal. In this it will be seen that the so-called negative glow not only follows the 
general contour of the disk, but that it projects through the aperture. This part of 
the discharge assumes the character of a positive column in a constricted tube, and 
exhibits the well-known bead-like striae. 
It has been already suggested in the text of this paper, that the long dark space 
intervening between the negative glow (or stria, as it is here regarded) and the head 
of the striated column is due to the local action of the terminal itself. An experiment, 
shown in Plate 20, fig. 29, corroborates this view. Beside the end terminals which 
were used for the discharge, the tube was furnished with an intermediate ring 
terminal, which remained disconnected, except so far as leakage through it from the 
air. The column of stride did not usually extend from the positive end so far as the 
ring. But when the column was drawn out by the influence of a magnet, and made 
fully to reach the ring, the column of striae was immediately thrown back, so as tc 
form a comparatively long dark space between the stria so anchored on the ring and 
the column behind. This sudden throwing back was repeated every time a stria was 
brought on to the ring by the magnet, and was doubtless due to the fact that the ring 
was acting as a (weak) negative pole through leakage from the air. 
B .—On the double character of the coil discharge. 
We have given experimental proof in Section XI. of this paper, that when we take a 
discharge of small quantity from a coil of symmetrical make, the electricity passes into 
the tube simultaneously at both terminals, and that the two discharges meet and form 
a neutral zone near the middle of the tube. Since the paper was originally written, 
the authors have met with cases in which the distinction between the nature of the 
discharges from the two terminals and the position of their place of meeting are of 
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