200 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
to occupy the unstained spaces ; the stains therefore marked the intervals, 
or cooler parts, . between former strata.'" The insertion of 500,000 ohms 
changed the colour of the strata to pink and the form to that shown in 
fig. 6, Plate 16, hut their position remained unaltered. This corroborates our 
experience with tube 148. 
Tube 133, 27 inches between the terminals, diameter P875 inch. 
Nitrogen. 
172. — Pressure 10 m.m., 13,158 M, 8040 cells. A nebulous light from the 
positive, extending half the length of the tube to the ring negative. 
173. — Pressure 6 m.m., 7895 M, 8040 cells. Five steady luminosities, quite 
uniform, without indications of strata, like 6, fig. 52, but, of course, shorter ; 
with 90.000 ohms gradually introduced the phase continued the same. 
174. - — Pressure 3 - 5 m.m., 4605 M. 4800 cells would not pass ; with 5880 cells, 
four luminosities. 
175. — Pressure 1*5 m.m., 1974 M, 3600 cells. Strata near the positive, as 
fig. 54. These were rather fuzzy, but were better defined with 300,000 
ohms introduced. 
Fig. 54. 
176. — Pressure 1 m.m., 1316 M, 3240 cells. Similar strata : with 2,570,000 
ohms, six luminosities. The discharge was red throughout the tube, except 
on the negative terminal, which was violet. 
* Gassiot (Brit. Assoc., 1869 (sect.), p. 46) : “ In one of Geissler’s tubes with which I have for some 
time experimented I obtained, by using my extended series of the voltaic battery, not only a very dense 
opaque deposit on the glass round the negative electrode, but five or six bands of dark deposit along the 
tube ; in carefully examining their position 1 find they exactly coincided with the dark band between the 
striae, that they did not increase in density by continuing the discharge like the deposit round the 
negative, but remained without further change. 
“ I have not any record from Geissler of the nature of the gas, &c., and have not been able to obtain 
similar results with other tubes obtained from Geissler. 
“ In one of Cam’s originally charged with arseniuretted hydrogen there was such a deposit. 
“ This result appeared to me to explain that the deposit in Geissler’ s tube did not arise from particles 
of the negative electrode but from the gas with which it was originally charged ; their being deposited 
exactly in the dark portions between the luminous disks may lead to a correct explanation of a 
phenomenon that has hitherto baffled the ingenuity of the experimentalist.” 
