To enable the voltaic spark to pass through air before the terminals of the battery were united, it was necessary to exalt the electro-motive force of the battery by multiplying its elements; but all the elements Faraday possessed were unequal to the task of urging the spark across the shortest measurable space of air.
Nor, indeed, could the action of the battery, the different metals of which were in contact with each other, decide the point in question.
Still, as regards the identity of electricities from various sources, it was at that day of great importance to determine whether or not the voltaic current could jump, as a spark, across an interval before contact.

Faraday's friend, Mr.Gassiot, solved this problem.

He erected a battery of 4000 cells, and with it urged a stream of sparks from terminal to terminal, when separated from each other by a measurable space of air.
The memoir on the 'Electricity of the Voltaic Pile,' published in 1834, appears to have produced but little impression upon the supporters of the contact theory.

These indeed were men of too great intellectual weight and insight lightly to take up, or lightly to abandon a theory.
Faraday therefore resumed the attack in a paper, communicated to the Royal Society on the 6th of February, 1840.

In this paper he hampered his antagonists by a crowd of adverse experiments.