186 
MESSES. W. DE LA RUE AND H. W. MULLER ON THE 
it, and then returned to it again to move slowly away, the current was 
still 0 ’00993 W. The calculated resistance of the tube at this pressure is 
688,900 ohms. 
78. — Pressure 10T m.m., 13,289 M, 8040 cells, C. 0‘00993 W. At first only a 
glow at both terminals, the tube became hot in the middle, a barely visible 
glow throughout the tube ; then one luminosity as shown on the left of 104, 
fig. 46, which travelled slowly to within 3 inches of the negative, and was 
followed by a second luminosity, as seen in the same figure. The O and F 
lines could be seen with the spectroscope in the glow around the negative 
terminal, the spectrum of a nebulosity was nearly continuous. 
79. — Pressure 10’2 m.m., 13,421 M, >8040 cells, C. 0’01158 W. One arrow- 
headed nebulosity, 105, fig. 46 ; the resistance of the tube was 570,000 
ohms. 
80. - — The tube in the same state; the induced current of Apps’s coil, No. 821, 
producing a 6 -inch spark, passed like the streamer discharge of the battery 
in air, as shown in Part I., page 88, fig. 16. The discharge in the tube is 
shown in fig. 47, which brings out strongly the effect of great difference of 
potential on the phenomena, and also supports the hypothesis that the dis- 
charge in partially exhausted tubes is of the same nature as through air at 
ordinary atmospheric pressure — a disruptive one.*' 
Fig. 47. 
TUBE 129. 
106 
81. — Pressure 8T m.m., 10,658 M, 8040 cells, C. 0’01331 W. 7 luminosities, 
part of them arrow-headed, arranged in a wavelike formation, the nebulosity 
nearest the positive entering one of the arrow-headed ones next to it, as shown 
107, fig. 46. The resistance of the tube was 477,000 ohms. 
82. — Pressure 6’8 m.m., 8947 M, 8040 cells, C. 0’0184 W. 10 nebulosities similar 
in character to 107, fig. 46. Resistance of the tube 304,900 ohms. 
83. — Pressure 4‘3 m.m., 5658 M, 5880 cells, C. 0’02371 W, resistance of the 
tube 175,100 ohms. 13 luminosities were obtained like fig. 7, Plate 15. 
The G, F, and C fines were visible in the glow around the negative terminal, 
but they were not visible in the nebulosities. 
84. — Pressure 1 m.m., 1316 M. 2400 cells passed, with 3600 the current was 
0'03251 W, the same phase as 85, fig. 46. 
* Gassiot (Phil. Trans., 1858, p. 5) describes a similar discharge as a wavy line. His tube, when 
cooled by a freezing mixture of ice and hydrochloric acid, gave strife. 
