ELECTRIC DISCHARGE WITH THE CHLORIDE OF SILVER BATTERY. 
221 
of the strata from the negative, whether the puff of gas entered from the 
negative or from the positive end.* 
The wires of this tube had been enclosed nearly up to their extremities in 
capillary glass tubes ; after repeated discharges these tubes fuzed and enclosed the 
wires nearly completely, only leaving a section of them free. When this had happened 
a very striking phenomenon was observed at the negative terminal on sending a current 
of 5120 cells through the tube, numerous sparks were thrown off from the extremity 
of the wire in a very thin sheet at right angles to the axis of the tube, producing the 
appearance of spokes of a wheel ; the discharge throughout the tube was not stratified. 
Not the slightest projection occurred either backwards or forwards in the direction of 
the length of the tube, showing that there is a lateral force existing at the negative 
terminal. The axial direction of the positive impulse, combined with the radial 
direction of the negative, at right angles to it, may play an important part in the 
production of stratification.! 
* De la Riye (Geneve Mem. Soc. Phys. xvii., 1863, p. 75) made similar experiments ; he intro- 
duced during the passage of a current in a vacuum a charge of the same gas that it contained, 
in quantities sufficient to lower the column of mercury £ or \ a millimetre. If the gas were intro- 
duced at the negative end striae well defined were immediately formed in the dark space of the same 
diameter (that of the tube) as the striae already existing, hut much closer and narrower. These gradually 
extended the whole length of the tube, entangling the original striae in their course. When the admission 
of gas had been stopped the luminous column gradually receded from the negative and the tube took up its 
normal appearance. If the gas were introduced at the positive end, instead of striae occupying the whole 
length of the tube a narrow jet of brilliant light was seen to advance along the axis of the tube in the 
interior of the luminous column, which immediately extended through the dark space near the negative. 
When the admission of gas had ceased the tube returned to its normal condition. In the same paper 
(pp. 73— 74) the author describes some experiments in which he had a gauge attached to the vacuum tube : 
the mercury column was observed to oscillate during the discharge through a range of, under favourable 
circumstances, 0'4 m.m. ; De la Rive considers that these two experiments support the opinion of Reiss, 
of Berlin, that these phenomena are purely mechanical. 
Spottiswoode showed a similar experiment at a recent meeting of the Royal Society. 
t Vak,ley (Proc. Roy. Soc., xix., 1871, p. 239) constructed a tube in which a slip of talc, 1 inch 
long, -Jq inch broad, and weighing ~o of a grain, was attached in the middle to a fibre of silk stretched 
diametrically across the tube ; the position of the vane was not between the terminals, two rings, hut 
between one end of the tube and one of them. When the discharge, which was in the form of an arch, 
passed between the two terminals no effect was produced on the vane ; when, however, the arch was 
influenced by an electro-magnet and made to play upon either the lower or upper end of the vane that 
part of the vane was repelled, no matter in which direction the current was passing, in some cases 
as much as 20°. The author states that in his opinion the arch is composed of attenuated 'particles of 
matter projected from the negative pole in all directions, but that the magnet controls their course. 
The view that the striae are aggregations of matter, and that their formation is a mechanical 
process, appears to receive some support from the fact described by Spottiswoode in a paper on the 
rapid-contact-breaker (Proc. Roy. Soc. xxiii., 1875, pp. 445-462). In the case of the double discharge 
the striae of the one discharge fit exactly into the spaces of the other, indicating thereby that the 
distribution of the residual gas at the close of one discharge is such as to favour a similar distribution in 
an immediately succeeding discharge, and that time is necessary for a fresh distribution. 
See also Appendix, note C. 
