Robert William Mylne (1816-90) from an early was a gifted scientist. He won the Telford bronze award when only 24. His family had a long connection with engineering, Blackfriars Bridge having been built by his grandfather Robert (1781-1863). Robert William’s particular interest was in the connection of water supply to geological structure. This work first published in 1851 was “the first really intelligent geological map of London, it was also the first London map with contours” (Hyde). The map extends from Hendon in the north west to East Wickham in the south east and bears below a section taken between those two points. The latter was added to the second state in 1858. Hyde (1975) no. 16, state 3 & pp. 31-4.