Führer durch das Eisenwerk Unterwellenborn bei Saalfeld a. d. Saale
A guidebook to the Unterwellenborn ironworks near Saalfeld on the Saale, written by A. Dürkop and published in 1892 by the Wiedemann bookshop for visitors touring the plant. Its pictures are plain black-and-white line diagrams of furnaces, a hot-blast stove with its gridwork and pipe connections, and a U-shaped vessel with a siphon-like tube, drawn in clean technical outline that suits schematic icons or process-flow graphics.
