The following notes are the result of experiments made by research students, under the direction of the author, on a 25-period single-phase Atkinson-type repulsion motor in the Laboratories of Applied Electricity, Liverpool University. The work involved in preparing Part I was carried out by O. J. Crompton, C. G. Ramsay and E. W. Young. That entailed in the preparation of Part II was performed by T. W. Dann.In the first place a vector diagram for the motor, in line with the standard diagram for a single-phase series commutator motor, has been developed. It is then shown how, by means of bruoh shifting, the motor may be made to operate as a generator.It is obvious that regenration by means of brush shifting has limitations in its practical application. To obviate these limitations regeneration with a fixed brush-position and a reversed field coil was investigated. This was found to be a function of the speed and could not be varied independently. Finally, by injecting an E.M.F. into the armature short-circuit, with fixed brush-position and reversed field, it has been found possible to control the amount of power regenerated at any given speed.