Paper, 'Note on the theory of the alternate current dynamo' by John Hopkinson Hopkinson writes: 'According to the accepted theory of the alternate current dynamo, the equation of electric current in the armature is γy + Ry = periodic function of t, where γ is a constant coefficient of self-induction. This equation is not strictly true, inasmuch as γ is riot in general constant, but it is a most useful approximation. My present purpose is to indicate how the values of γ and of the periodic function representing the electromotive force can be calculated in a machine of given configuration.' Annotations in pencil and ink throughout. Includes one diagram of Hopkinson's proposed dynamo. Subject: Physics / Electricity Received 17 February 1887. Read 10 March 1887. A version of this paper was published in volume 42 of the Proceedings of the Royal Society as 'Note on the theory of the alternate current dynamo'. 1887