Müschenbroek’s Wonderful Bottle

In his second letter to Mr. Collinson, Franklin presented his one-fluid theory of electricity. Contrary to Du Fay’s two-fluid theory, Franklin suggested that all objects contain within them a certain quantity of the so-called “electrical fire”. While the overall quantity of this electrical fire is unchanged—it is a conserved quantity—its distribution need not be uniform everywhere. Objects having a (perhaps temporary) surplus are said to be “plus”; objects having a deficit are said to be “minus”. Such charge separation commonly occurs with friction between different objects, as when glass is rubbled with silk (the glass becomes “plus” and the silk becomes “minus”), or amber with fur (the amber becomes “minus” and the fur becomes “plus”). In this way, Franklin was able to account for many electrical phenomena by introducing the concept of positive and negative electricity. At this point, you might pause to consider whether (or to what extent) Franklin’s theory of electricity is different than the modern view. Now, in his third letter to Mr. Collinson, Franklin deploys his one-fluid theory so as to understand the working of “Mueschenbroek’s wonderful bottle”. Where might the bottle store its electricity when electrified? In the water? In the glass? In the central wire?