188 
MESSES. W. DE LA RUE AND H. W. MULLER ON THE 
92. — Pressure 0'5 m.m., 658 M, the current of 2400 rod-cells passed. With 3600, 
C. 0 '03071 W, there was a nebulous discharge from the positive almost 
reaching the negative, near which a few strata were formed. On disconnect- 
ing the battery the gas in the tube was observed to be phosphorescent and 
the phosphorescence continued for 6^ seconds.* The nebulous discharge 
was salmon coloured, not at all like the red discharge of a nitrogen vacuum. 
93. — Pressure had increased without leakage to 0'6 m.m., 789 M, 2400 cells, with 
200,000 ohms resistance, C. 0 '00 52 7 W. There were produced, commencing 
at the positive wire, 21 well defined and perfectly steady strata, about 1 inch 
thick, like c, fig. 43, very bright at the convex face : the glow round the 
negative was cylindrical. The resistance of the tube was reproduced by the 
insertion of 90,000 ohms in place of the tube. 
Tube 130, Air. 
94. — Tube 130, charged with air and exhausted to a pressure of 8 m.m., 10,526 M, 
8040 cells. One luminosity from the ring when positive, about 12 inches 
long. 
95. — Pressure 4 m.m., 5263 M, 8040 cells. A continuous nebulous discharge, 
carmine in colour, from the point positive, reaching nearly to the negative 
where there was formed a separate luminosity, as represented in 1 , fig. 48 ; 
with 200,000 ohms in circuit, the nebulous discharge from the positive 
separated into two luminosities making, with that at the negative, three 
in all. 
Fig. 48. 
TUBE ISO AIR 
96. — Pressure 3'5 m.m., 3605 M, 8040 cells. Strata were produced as in 2, fig. 48, 
but the discharge was confused in the greater part of the tube. 
* Gassiot (Dec. 1858 — Phil. Trans. 1859, p. 137) says, “ in some tubes (Geisslee’s) for several 
seconds after the discharge had ceased the tubes remained throughout their entire length phosphorescent.” 
About the same time Becquerel, whose attention had been directed to this phenomenon by 
Ruhmkorff, communicated the result of his observations to the Academie des Sciences (‘ Comptes 
Rendus,’ xlvii., 1859, pp. 404-406). The subject has since been investigated and discussed by Morren 
0 Comptes Rendus,’ liii., 1861, pp. 794-795) ; Sarasin (Archives Sci. Phys. Nat. xxxiv., 1869, pp. 243- 
254; Ann. de Chim. xvii., 1869, pp. 501-502; Poggend. Annul, cxl., 1870, pp. 425-434) ; De la Rive 
(‘ Comptes Rendus,’ lxviii., 1869, 1237-1238; Ann. de Chim. xix., 1870, pp. 191-192) ; Hittorf (Ann. de 
Chim. xvii., 1869, pp., 487-496), and others. 
