On This Day in Trinity House History – 20 June

1800

Trinity High Water Mark is established along the Thames

Trinity High Water Mark: The datum which is referred to in connection with soundings in the River Thames originated in

“An Act for making Wet Docks, Basins, Cuts and Other Works, for the greater Accommodation and Security of Shipping, Commerce, and Revenue, within the Port of London”

Their depth was “to be within fifteen inches of Low Water Mark as settled by two Elder Brothers of the Trinity House.”

Sir James Douglass Engineer-in-Chief

Sir James Douglass Engineer-in-Chief

Exactly 65 years later, Sir James Douglass, Trinity House’s Engineer-in-Chief and famed lighthouse builder, reporting to the Board stated:

“I have had a careful examination made of the Wharfs along the North side of the River, between the Hermitage and Shadwell Entrances of the London Docks, but only one stone has been found. This stone is fixed in the face of the River Wall on the East side of the Hermitage Entrance of the London Docks, and has the following inscription, ‘Low Water Mark is Seventeen Feet 10 inches below the lower edge of this stone, settled by the Corporation of the Trinity House August 1800.’ Cast Iron Plates were found on the West side of the Wapping Entrance and the East side of the ShadweII Entrance of the London Docks… I find that these Plates were fixed, with 54 others, in the year 1853, by the Thames Navigation and Port of London Committee at various places along the banks of the River, commencing at Cadogan Pier, Chelsea and terminating at Woolwich Dockyard. The Trinity High Water Line on these Plates was carefully levelled from the lower edge of the old stone at the Hermitage Entrance of the London Docks, which is 12.50 feet above Ordnance Datum, or Mean Half-tide Level at Liverpool.”

The level of the now-defunct Trinity High Water or Trinity Standard was deemed to be 11.4 feet above the datum line called mean sea level at Newlyn in the County of Cornwall in the Second Geodetic Levelling of England and Wales published by order of the Minister of Agriculture, Fisheries and Food.

Cast iron plates were found on the West side of the Wapping Entrance and the East side of the Shadwell Entrance of the London Docks. 54 plates were fixed in the year 1853 by the Thames Navigation and Port of London Committee at various places along the banks of the River commencing at Cadogan Pier, Chelsea and terminating at Woolwich Dockyard. The Trinity High Water Line on these Plates was carefully levelled from the lower edge of the old stone at the Hermitage Entrance of the London Docks, which is 12.50 feet above Ordnance Datum, or Mean Half-tide Level at Liverpool.

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