506 
Proceedings oj the Royal Society 
evolution of gas is immediately arrested over the entire surface of 
the electrode. The same plate, free from hydrogen, when brought 
in contact with a platinum electrode evolving hydrogen, shifted the 
evolution of gas only on the same side on which it was firmly 
pressed. In order to examine the action of mixed electrodes, the 
palladium plate was welded with a similar platinum plate into a 
V shaped electrode, when the apex of the combination could be 
placed in or out of the liquid. If the platino-palladium electrode 
is made the negative pole, hydrogen makes its appearance imme- 
diately on the platinum plate ; no gas is evolved by the palladium 
for some time. If, after saturation, by reversing the poles, oxygen 
is thrown on the mixed electrode, no gas is evolved from the 
platinum, and when the gas began to be evolved, it appeared 
simultaneously on both plates. The same result is observed what- 
ever may be the position of the compound plate relatively to the 
other pole in the liquid, relative distance from the other pole having 
no effect. This proves that the whole of the oxygen that ought to 
be evolved on the platinum is transferred by a polar chain, through 
the liquid, on to the palladium plate, so long as this plate contains 
occluded hydrogen. The presence of the strong electric current 
is shown by connecting the hydrogenised palladium with a platinum 
plate in an acid liquid, the circuit containing a galvanometer. If 
the apex of the Y electrode is placed in the acid liquid additional 
phenomena are witnessed, depending upon which side of the com- 
pound electrode is next to the other electrode. If the platinum 
side of the Y electrode is firmly clipped in a stand, a glass rod keep- 
ing the apex in the same position in the liquid, and if the palladium 
plate is next to the positive electrode, we observe the following 
change during the course of the hydrogenation. The angle of the 
Y continually diminishes by the motion of the palladium towards 
the perpendicular, the hydrogen evolved coming only from the 
outer surface to the compound plate. After some time the plate 
returns to its original position, and would curve beyond it if the 
action was continued. If oxygen is now evolved on the compound 
plates, the first effect of the oxygen is to curve it beyond its first 
position, or to increase the angle of the Y. If the palladium plate 
was furthest from the positive electrode, the first effect of the 
hydrogenation is to increase the angle of the compound plate by 
