Paper, 'On the potential difference required to produce a spark between two parallel plates in air at different pressures' by J B Peace Peace writes: 'The following is an account of an investigation into the relations between potential difference, spark-length, and pressure when discharge takes place between two parallel plates in air. The investigation was undertaken at the suggestion of Professor J J Thomson, and has been carried out in the Cavendish Laboratory in Cambridge.' Annotations in pencil and ink. Includes eight pages of diagrams of experimental apparatus and results. Subject: Physics / Electricity Received 24 May 1892. Read 16 June 1892. Communicated by Thomson. A version of this paper was published in volume 52 of the Proceedings of the Royal Society as 'On the potential difference required to produce a spark between two parallel plates in air at different pressures'. 1892