Witchcraft trials of 1730

I read recently of witchcraft trials in Mount Holly in NJ in 1730 in which a witch and a wizard were put on "trial".  The townspeople, in an effort to be fair, choose two of their number to undergo the same "tests" as the suspected witches "as a sort of litmus test to prove their fairness".  The four were all stripped naked and tied hand and foot and dropped into a pond.   "It was thought that anyone who was a witch would float on the surface of the water, while an innocent would sink to the bottom".  One of the test persons sank while the   other and the two accused floated to the surface.  There was no further indication of what happened next.  I think the interesting point here is that an account of this was recorded by one "Benjamin Franklin" who as "an enlightened thinker of his day...poke fun at folk beliefs which still persisted as well as to have a joke at the expense of Burlington County residents, whom Philadelphians saw as rustic, rural yokels".  I post this because I wonder if the "test" we have always heard about-the sinking in water when dunked-was in fact made up by this "Benjamin Franklin" just to ridicule those who believed in witches.  I am also assuming that the Benjamin Franklin noted here is the one history books record the existence of.
(Source: "The Mount Holly Witch Trials of 1730" by Michael Vikovic in Weird New Jersey volume number 19.  This source is questionable; I have no knowledge of the magazines value as a source of history).