What is "verticity"

Verticity \Ver*tic"i*ty\, n. [Cf. F. verticit['e]. See Vertex.] The quality or power of turning; revolution; rotation. [R.]
--Locke.

I hardly believe he hath from elder times unknown the verticity of the loadstone.
--Sir T. Browne.

n. The quality or power of turning; revolution; rotation.

In the history of physics, verticity (Latin: verticitate) is a tendency to move around or toward the North or South Pole, often called Earth's "vertices". During the English Renaissance, some thinkers blamed verticity for the behavior of magnets. Francis Bacon believed that verticity was spread amply throughout the cosmos, and used verticity to explain the motion of oceans, winds, and even celestial bodies.

Bacon formulated his unusual theory partly in response to the acclaimed 1600 treatise On the Magnet and Magnetick Bodies, and on That Great Magnet the Earth, written by William Gilbert. Gilbert discussed two kinds of verticity. Surface verticity is a tendency to point north. It is found in ordinary "loadstones" and magnetised iron. This verticity was a weaker expression of a far more powerful sort of verticity intrinsic to the core of the Earth, which Gilbert called deep verticity. Gilbert was among the first to believe that the Earth spun, and attributed this spinning to Earth's 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 having been corrupted and weakened by exposure to the degraded matter of Earth's crust. These bits of matter became the variety of weak magnets found nearer the Earth's surface. So Gilbert thought.

Bacon rejected much of Gilbert's magnetic theory. He denied that Earth spun, and he denied deep verticity. Earth's core was cold, passive, and unmoving, as Telesio had said. The Earth was not magnetic. To explain verticity of magnets, Bacon argued that we needn't look below the surface of the Earth but should instead look up, to the behavior of winds and celestial bodies. The tendency that magnets have to rotate westward (as Bacon conceived it) was only a special case of a general tendency of things to move westward around Earth's core, a tendency exhibited by all things save the core itself. The Atlantic Ocean rolled westward and ricocheted off the Eastern coast of the New World, creating the tides. The planets, stars, sun and moon moved westward across the sky. The rotation of magnets was simply a weak manifestation of the same kind of westward migration undertaken daily by sundry objects on Earth and in the heavens.

An open question is why Bacon was moved to give a unified account of the motion of magnets and other natural movers. Graham Rees tentatively suggested (2006, p. liii) that Bacon tended to conceive related occurrences as part of a spectrum. It might have seemed to Bacon that magnets are part of a continuum encompassing the unturning Earth as well as the rotation-prone magnets on Earth's surface and the westward-hurtling planets above.