Mapping observatory on top of St Paul’s Cathedral

Victorian illustration to download showing a small temporary observatory perched on the cross on top of St Paul’s Cathedral. The hexagonal observatory, made of wood with a canvas roof, sits on a railed platform supported by wooden scaffolding and can be reached by a ladder. Inside the observatory a soldier uses a theodolite to make observations for mapping purposes. This observatory was built in 1848 as part of the Ordnance Survey’s project to map Great Britain at a scale of 6 inches to a mile; the project was undertaken by the Royal Engineers.