“- 
193 
power 
ess when chemically inactive. 
One of the very few experimental mistakes of Faraday oc- 5 
curred in this investigation. He thought that with a single 
voltaic cell he had obtained the spark before the metals touched, 
but he subsequently discovered his error. To enable the voltaic ae 
spark to pass through air before the terminals of the battery 
were united, it was necessary to exalt the electro-motive force _ 
? 
& stream of sparks from terminal to terminal, when separated 
from each other by ameasurable space of air, 
. the memoir on the “ Electricity of the Voltaic Pile,” pub- 
hed in 1834, appears to have produced but little impression 
iy the supporters of the contact theory. These indeed were 
f 
UP; Or lightly toabandonatheory. Faraday therefore resumed 
difficulty after difficulty about the neck of the contact theory, 
Until in its efforts to nota from his assaults it so changed its 
r e 
frbosed by Volta. The more persistently it was de U 
