'The Scaffolding and Observatory on St. Paul's in 1848', (1897). Observation post built by officers of the Royal Engineers on top of the cross on St Paul's Cathedral in London. Triangulation measurements were taken from here in order to make a new map of London. The map was used to plan drastic improvements to the methods of drainage and sewage disposal, in order to prevent cholera epidemics in the capital. From Old and New London, Volume I, by Walter Thornbury. [Cassell and Company, Limited, London, Paris & Melbourne, 1897]