Definition of Polhode

The polhode is the non-plane curve traced on the surface of an ellipsoid with fixed center by its point of contact with a fixed plane on which it rolls, as in the revolution of a top.

-- Oxford English Dictionary

Hence the jabberwockian sounding statement: the polhode rolls without slipping on the herpolhode lying in the invariable plane

-- Herbert Goldstein, Classical Mechanics

The corresponding line on the plane is the herpolhode.

A short poem about polhodes and herpolhodes by David N. Williams.

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