Diagrams and photographs, 'Discharge through mercury vapour' by Arthur Schuster 21 photographs and six diagrams in pencil showing the process of electrical discharge through mercury vapour in a small vessel into which an electromagnet is introduced. Subject: Chemistry / Electricity Some of these diagrams were published in volume 37 of the Proceedings of the Royal Society alongside the paper 'The Bakerian Lecture. Experiments on the discharge of electricity through gases. Sketch of a theory'. 1884