'Be one thing or the other,' he seemed to say to an unproved hypothesis; 'come out as a solid truth, or disappear as a convicted lie.' After making the great discovery which I have attempted to describe, a doubt seemed to beset him as 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.