At 17, he discussed the question of the materiality of heat with his Quaker friend and mentor Robert Dunkin. Dunkin remarked: I tell thee what, Humphry, thou art the most quibbling hand at a dispute I ever met with in my life. One winter day he took Davy to the Lariggan River to show him that rubbing two plates of ice together developed sufficient energy by motion to melt them, and that after the motion was suspended, the pieces were united by regelation. It was a crude form of analogous experiment exhibited by Davy in the lecture-room of the Royal Institution that elicited considerable attention. As professor at the Royal Institution, Davy repeated many of the ingenious experiments he learnt from Dunkin.