4S4 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
Inch. 
0-44 
0-45 
0-46 
Mean . . 0*45 (1*1 cenfcim.) 
In air saturated with moisture 0'45 
Mean . . 0*447 (1*1 centim.) 
From these experiments we arrive at the conclusion that the striking distance is the 
same in dry air as in air saturated with moisture. 
Two separate currents in the same tube. 
Several experiments were made in a specially constructed tube with the object of 
ascertaining the mutual effect of two discharges passing within it first in the same 
and then in a contrary direction. 
Tube 347 consists of an outer tube If inch (4*4 centims.) in diameter, 31 inches 
(78*7 centims.) long, and 27-g- inches (69*8 centims.) between the terminals, two short 
pieces of tube, 9 inches (22*8 centims.) long and f inch (1*27 centims.) in diameter, are 
fixed one at each end ; the distance between the open mouths of the small tubes being 
13 inches (33 centims.) (see fig. 10). 
Fig. 10. 
Two paraboloidal terminals are sealed in the outer tube and two precisely similar 
ones are sealed in the small tubes and hold them in then* places. 
When the discharge from a battery of 3600 cells was made to pass through the 
small tube a close stratification, as in Plate 35, fig. 1, was produced, which stratifica¬ 
tion was continued in the interval between the open ends of the small tubes, but of 
an altered form, wider apart as shown in the figure, which is a facsimile of a photo¬ 
graph obtained on a dry plate in one second, 
When the same discharge passed through the outer large tube a continuous stratifi¬ 
cation was obtained throughout, as shown in Plate 35, fig. 2. 
When the discharges from two separate batteries, each of 3600 cells, were made 
to pass in reverse directions, the one in the outer tube having an external resistance 
of 250,000 ohms inserted, the discharge in the small tubes was the strongest, and an 
appearance was produced as shown in Plate 35, fig. 3. 
It will be noticed that the effect of this stronger discharge is to completely reverse 
the convexity of the strata in the middle portion of the outer discharge in the large 
tube, while the convexity on the two extremities of the outer discharge retains its 
