Paper, 'On an instrument for indicating and measuring difference of phase between E M F and current in any alternating current system' by Philip Cardew Cardew writes: 'If the periodic time of an alternating E. M. F be T, and if, owing to the presence of capacity or self-induction, or both in the circuit, the current passes through the value 0 at times differing from the times of passage of the E. M. F. through the same value by t, the electrical power will be V × C × cos (2πt/T), where V indicates the effective volts and C the effective current.' Annotations in pencil and ink. Subject: Electricity Received and read 21 June 1894. Communicated by Lord Kelvin [John William Strutt]. A version of this paper was published in volume 56 of the Proceedings of the Royal Society as 'On an instrument for indicating and measuring difference of phase between E. M. F. and current in any alternating current system'. 1894