"I have observed an interesting N type negative resistance effect that happens only when the tip of a very sharp aluminum electrode is just barely touching the top surface of the solution."

What exactly does negative resistance mean in this context? Based on the curve shown I would guess as the voltage increases past a point the resistance decreases. But it is fun to imagine this guy has discovered perpetual energy.

update: of course there is a wikipedia page. https://en.wikipedia.org/wiki/Negative_resistance