196 MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
In consequence of a crystalline deposit having formed in the tube it was 
detached from the pump in order to ascertain its nature : it was insoluble in 
bisulphide of carbon, water, alcohol, nitric, hydrochloric, or strong sulphuric 
acids, but by heating the tube with a spirit lamp, a little strong sulphuric 
acid having been previously inserted, the substance came off in yellow flakes 
and proved to be sulphur which was now soluble in bi-sulphide of carbon. 
It had existed in the first instance in one of its allotropic conditions. It 
was ascertained that the source of the sulphur was the vulcanized india- 
rubber junction tube from which it was gradually taken up by the current 
of hydrogen. This tube was replaced by another, 0‘4 inch in diameter with 
O'l inch bore, made of ordinary india-rubber, but it was found necessary, not- 
withstanding its thickness, to support it by the insertion of a helix of 
platinum wire 0'0125 inch in diameter. 
Tube 132, Air. 
26 inches between the terminals, 1 ■'75 inch diameter. 
150. — Pressure 13 m.m., 17,105 M, 8040 cells would not pass ; pressure 11*6 m.m., 
15,263 M, the current just passed. 
151. — Pressure 9‘3 m.m., 12,237 M, 8040 cells. A faint glow about 6 inches long 
when the ring was positive. 
152. — Pressure 6‘3 m.m., 8289 IW1. 8040 cells passed at first and several 
luminosities emanated from the positive, hut after a while they disappeared 
and could not be reproduced. The illumination was feeble but the amount of 
heat generated was great in proportion to the light. 
153. — Pressure 6 m.m,, 7895 M, 8040 cells. Six luminosities were produced 
when the ring was positive, as shown in 1, fig. 52. 
Pig. 52. 
154. — Pressure 4'9 m.m., 6447 M, 6840 cells. Four similar luminosities, 1, fig. 52, 
which were reduced to two on introducing 500,000 ohms into the circuit. 
These luminosities issued at the rate of about one per second from the posi- 
tive, and when there were three, the middle one approached that emanating 
