In the history of physics, verticity (Latin: verticitate) is an alleged tendency to move around or toward the North or South Pole, often called Earth's "vertices". In his acclaimed 1600 treatise On the Magnet and Magnetick Bodies, and on That Great Magnet the Earth, William Gilbert distinguished two kinds of verticity. Surface verticity is the tendency to point north found in ordinary "loadstones" and magnetised iron. This verticity was the weaker expression of a more powerful kind of verticity: the deep verticity in the Earth's core. Gilbert was among the first to believe that the Earth spins. It spins, he says, because of its deep verticity. In his judgement, deep verticity also explained surface verticity: over time, bits and pieces of matter escaped from Earth's core, their verticity h