Plates, relating to 'An account of operations carried on for ascertaining the difference of level between the River Thames at London Bridge and the sea; and also for determining the height above the level of the sea, &c. of intermediate points passed over between Sheerness and London Bridge' by John Augustus Lloyd Unpublished map and diagram relating to Lloyd's paper titled 'An account of operations carried on for ascertaining the difference of level between the River Thames at London Bridge and the sea; and also for determining the height above the level of the sea, &c. of intermediate points passed over between Sheerness and London Bridge'. Observations from this paper are found at PT/19/10. Subject: Hydrography [1830]