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This brief preliminary report shows by a simple experiment that major flux changes in tape‐wound, magnetic‐amplifier‐type cores begin near the core's inner perimeter and progress outward, at power frequencies, as has been predicted [R. C. Barker, Trans. Am. Inst. Elec. Engrs. 79‐I, 482 (1960), with accompanying discussion]. It also shows, when the core is operated on a minor hysteresis loop, that at the start of every odd half‐cycle of excitation additional small inward‐progressing flux changes occur near the outer boundary of the region in which flux was reversed during the preceding even half‐cycle. This reduces slightly the hysteresis loss in the odd half‐cycles, and the resulting energy unbalance causes the minor loop to cling to one end of the major loop—a phenomenon well known in rectangular‐loop materials. The cause of the energy unbalance was hitherto unknown, however. The method used for the experiments is observation of the voltage that appears between two probes touched to the side of the core when the core is excited by a conventional winding. This method is known to other investigators but scantily reported in the literature. It is not analyzed here, but some experimental justification is given.