regards the identity of electricities. 'Is it right,' he seemed to ask,
'to call this agency which I have discovered electricity at all?
Are there perfectly conclusive grounds for believing that the
electricity of the machine, the pile, the gymnotus and torpedo,
magneto-electricity and thermo-electricity, are merely different
manifestations of one and the same agent?' To answer this question
to his own satisfaction he formally reviewed the knowledge of that day.
He added to it new experiments of his own, and finally decided
in favour of the 'Identity of Electricities.' His paper upon this
subject was read before the Royal Society on January 10 and 17, 1833.

After he had proved to his own satisfaction the identity of
electricities, he tried to compare them quantitatively together.
The terms quantity and intensity, which Faraday constantly used,
need a word of explanation here. He might charge a single Leyden jar
by twenty turns of his machine, or he might charge a battery of ten
jars by the same number of turns. The quantity in both cases would
be sensibly the same, but the intensity of the single jar would be
the greatest, for here the electricity would be less diffused.
Faraday first satisfied himself that the needle of his galvanometer
was caused to swing through the same arc by the same quantity of
machine electricity, whether it was condensed in a small battery or
diffused over a large one. Thus the electricity developed by thirty
turns of his machine produced, under very variable conditions of
battery surface, the same deflection. Hence he inferred the
possibility of comparing, as regards quantity, electricities which
differ greatly from each other in intensity. His object now is to
compare frictional with voltaic electricity. Moistening bibulous
paper with the iodide of potassium--a favourite test of his--and
subjecting it to the action of machine electricity, he decomposed