feeble movement of the needle always occurred at the moment when he
made contact with the battery; that the needle would afterwards
return to its former position and remain quietly there unaffected by
the flowing current. At the moment, however, when the circuit was
interrupted the needle again moved, and in a direction opposed to
that observed on the completion of the circuit.

This result, and others of a similar kind, led him to the conclusion
'that the battery current through the one wire did in reality induce
a similar current through the other; but that it continued for an
instant only, and partook more of the nature of the electric wave
from a common Leyden jar than of the current from a voltaic battery.'
The momentary currents thus generated were called induced currents,
while the current which generated them was called the inducing
current. It was immediately proved that the current generated at
making the circuit was always opposed in direction to its generator,
while that developed on the rupture of the circuit coincided in
direction with the inducing current. It appeared as if the current
on its first rush through the primary wire sought a purchase in the
secondary one, and, by a kind of kick, impelled backward through the
latter an electric wave, which subsided as soon as the primary
current was fully established.

Faraday, for a time, believed that the secondary wire, though
quiescent when the primary current had been once established, was
not in its natural condition, its return to that condition being
declared by the current observed at breaking the circuit. He called
this hypothetical state of the wire the electro-tonic state: he
afterwards abandoned this hypothesis, but seemed to return to it in
later life. The term electro-tonic is also preserved by Professor