Thewestward driftof surface geomagnetic patterns (the rate of which is about 30° of longitude per century) has at least one superimposedrotationof period ∼480 years (Fig. 1), and possibly another of period ∼800 years; these are phenomena of a peculiarly localized nature. The 480‐year rotation is demonstrable not only in the curves of declinationversusdip, but also in the isoporic patterns. A strongpulse‐disturbancewhich occurred in the relative rotation of the terrestrial core, and therefore in the westward drift, is shown to affect the 480‐year rotation in a manner which helps to clarify the rel