98 
MESSRS. W. DE LA RUE AND H. W. MULLER ON" THE 
Beads still formed on the positive, the light became so faint an inch or two from the 
positive as to be barely visible, H, fig. 84, reduced to one-third. 
Distance. 
Pressure. 
Depression. 
Ratio of 
increased to 
normal pressure. 
Current. 
inches. 
M. 
m.m. 
W. 
ratios. 
0-225 
1,003,685 
, , 
0-02456 
1-93 
0-450 
446,053 
o-i 
1-0002 
0-02371 
1-86 
0-675 
336,842 
0-5 
1-002 
0"02456 
1 93 
0-900 
335,526 
0-5 
1-002 
0-02544 
2 00 
1-125 
264,211 
. . 
0-02634 
2-07 
2-250 
215,921 
, , 
0-02056 
1-62 
5-520 
81,316 
, # 
, , 
0-01272 
1-00 
5-520 
3026 
(with 2400 rod cells) 0-08933 
7-02 
The arc in hydrogen between two points. Temp. 16°*2 C., 10,940 cells. 
Distance 0*75 inch, pressure 745 m.m., 980,263 M, current 0*01575 W, the 
appearance is represented in Plate 8, figs. 21 and 22, the first copied from a 
photograph obtained in 5 seconds, the second in 15 seconds. The central spindle 
breaks into a brush-like form towards the negative, there is then a dark interval 
between it and the glow on the negative. 
Distance 0*9 inch, pressure 745 m.m., 980,263 M, the discharge passed inter¬ 
mittently, so that the current could not be read off on the galvanometer. The 
appearance is represented full size in Plate 8, fig. 26, from a drawing. 
Distance 0'9 X 2, l - 8 inch, pressure 385*6 m.m., 507,368 M, current 0'01575 W, 
depression 14 m.m., total pressure 399'6 m.m., ratio of increased pressure 1'04. 
Plate 8, fig. 23, from a photograph in 13 seconds. The distance between the 
brush-like termination of the central spindle and the glow on the negative has 
relatively increased. Figs. 27 and 28 are other representations copied from drawings. 
Distance X 3, 2*7 inches, pressure 317*8 m.m., 418,158 M, current 0*00580 W, 
depression 13 m.m., total pressure 330*8 m.m., ratio of increased pressure 1'04. 
Plate 8, fig. 24, from a photograph in 15 seconds. The central spindle relatively 
still shorter. At times only the terminals were illuminated, but sometimes strata 
formed on the positive terminal. Fig. 29 is another representation copied from a 
drawing. 
Distance X 4, 3*6 inches, pressure 170*5 m.m., 224,342 M, 6300 cells, current not 
measured, the appearance is represented in Plate 8, fig. 25 ; the central spindle has 
decreased relatively still more. 
Distance X 7, 6'3 inches, pressure 85*8 m.m., 112,895 M, 10,940 cells, current 
0*01393 W, only a glow on both terminals, the intermediate discharge being dark. 
Distance 6*3 inches, pressure 10 m.m., 13,158 M, 10,940 cells, current 0*02456 W, 
