Diagrams, experimental equipment and results by Thomas Andrews Three diagrams: a graph labelled 'current between two bright "passive" bars of the same composition, one in warm, the other in cold nitric acid' and two schematic diagrams of the apparatus used by Andrews in his investigation into the passive state of iron and steel showing a U-shaped pipe connected to a galvanometer. Subject: Metallurgy Prints of these diagrams were published in volume 49 of the Proceedings of the Royal Society alongside the paper 'The passive state of iron and steel. Part II'. 1890