178 Prof. Oliver Lodge-on the Seat of the 
seems necessary to quote his own grounds for it, and I do 
so in a footnote”. 
Fig. 11.—Von Zahn’s Apparatus for experimenting in different Gases at 
different Pressures and Temperatures, and also in high Vacua. 
The upper plate, M, is attached by glass rods to a sledge, H, which slides 
on vertical steel rods, G, being pulled up by a string. On reaching its 
highest point it comes into contact with an insulated platinum wire, 8, 
which communicates with a Hankel electrometer through one of the 
insulated exits, R. The bottom plate is supported on the ring, HE. 
T is the stopcock for exhaustion and change of gas. Fig. 2 shows the 
appendage to the bottom plate for warming it by a current of steam. 
Fig. 3 shows the apparatus used for high vacua. The two plates are 
zinc and platinum, and the platinum is arranged to fall by its own 
weight when the whole thing is inverted. The diagram shows it in 
its highest position, and just going to fall back into its dotted position. 
The friction of its guide-rod seems not wholly satisfactory. 
* “ Andere etwas bessere Beobachtungsreihen gaben ahnliche Werthe. 
Bei allen war die Kleinheit von C. (the apparent Volta effect Zn/Pt) 
auffallend. Nun stellt ja dieser Werth, wie oben besprochen, nicht die 
Potentialdifferenz Zink-Platin dar, fiir seine Kleinheit muss aber eine 
anderweite Ursache vorliegen. Dieselbe kann ich zunichst nur darin 
finden, dass die Zinkplatte bei Anfertigung und weiterer Behandlung des 
Apparates sichtbar angelaufen ist (auf der einen Hilfte sogar blaue Far- 
bung angenommen hat). 
‘His liesse sich allerdings vermuthen, dass diese offenbar zu geringe 
