A roadside water trough, located in Forsyth Road, West Jesmond, Newcastle Upon Tyne, a few yards from the junction with the Great North Road.
An Ordnance Survey bench mark – a horizontal line with an arrow pointing up from below – is carved into one end of the trough.
These marks were cut by Ordnance Survey levelling staff to provide a network of points at which height has been precisely measured (to the centre of the horizontal line) above sea level.
There used to be about half a million bench marks in Great Britain but they are not needed any more, due to satellite technology, and about half have disappeared.
More photos/info in the Water Troughs In North East England thread at the Holy Wells & Water Lore Forum – http://holywells.boardhost.com/viewtopic.php?id=200