Photograph Piece Shot that day: Title. MillenniumLock
This was taken just a short wander west along the same bank as the caisson, looking across at the Millennium Dome.
The 1806 caisson dry dock gate on the Thames at Bow Creek.
Well, 1806 is a date, possibly the wrong date, in fact; it may well have been constructed many years earlier. Suggestions go back to 1779 because thats when this dock (one of four, all now gone) were originally built.
As you can tell I’m awestruck by this odd construction, the simplicity of design providing such a useful but difficult function grabbed my imagination and my love of engineering…
So I started digging. The main problem with trying to track down a date for this caisson is that it may not be the original gate! One of the useful aspects of using a floating caisson is that you can float it for use elsewhere so this caisson may well have come from any one of the hundreds of dry docks around at that time… or not… and have been adapted to fit this dry dock, a very common practice at the time.
A caisson, in case your wondering, can be described as a self-supported water tight structure designed to be used in or under water. Often used as a workspace for men building underwater, a temporary or permanent support, or like this one, a simple floating vessel that could be sunk and re-floated and used to dam a dry dock. (further description at Wiki)
This marvel of engineering as I like to call it, is an open top type, and can be found on the Thames near the outlet for Bow creek. If you open the link you can clearly see the curve of it via a Google map overview. (Link Googlemaps)
This caisson was refurbished around 1860 with wrought iron at the nearby Thames Iron works ( The origins of the West Ham United football team. Link to a WHU Stadium photograph in my gallery.) Its renovation is described in the London 1865 survey as ‘new and as having been fitted at the entrance within a few years.’ The same source describes the shape and size of the dry dock behind the caisson as being 272ft long, 55ft wide and 20ft deep, with timber lined sides and similar base with a curved brick head completing the other end of the dock.
Caissons used for gates like this were cunningly fabricated underneath to seal the entrance against leaking and provide a reliable way to secure the gate against further movement caused by the huge weight of a tidal Thames pushing to and fro from one side.
A ridge would be attached to the caisson running underneath, from left to right. Correspondingly a mirror of the ridge made as trough would be cast into the entrance’s brickwork, possibly using fresh clay as well, and again along the base and both sides. At full tide, the dock full of water, and a suitable ship fully moored within the dock, the empty caisson would be floated into position at the entrance. As it was filled with water via huge inlets direct from the Thames (you can see the one remaining inlet in the top shot), the caisson would sink down, guided by the ridge and trough until eventually once fully filled, it sat slotted and sealed into the entrance. Once filled the dock could be emptied naturally as the river flowed out on the next low tide via the two large outlets at the base of the caisson.
Article References.
British History Online Other leads for the history of this caisson including a photograph taken in 1986.
Trinity Buoy Wharf Historical Interest, River Access, Lighthouse.
Orchard Place, Bow Creek. (British History) Location, Ownership, Local History.
I Also found this great image of a Caisson being constructed as a working space for the Blackwall Tunnel nearby. From Tower Hamlets Council Archives. Small pdf Here Its very quick to load.
Interesting source - www.bruzelius.info’ ‘Quotation’ - In 1835-6, the well-known firm of Messrs. Ditchburn and Mare commenced iron shipbuilding on the Thames, which they carried on for many years in Bow Creek, the site of the present Thames Iron Works, and at a later period were followed by Messrs. David Napier, Samuda Bros., M. and H. L. Wigram, Miller and Ravenhill, Robinsons and Russell (afterwards the well-known firm of J. Scott Russell and Co., who built the “Great Eastern,” and whose premises included those formerly occupied by Messrs. Fairbairn and Napier), Joyce, Dudgeons, Rennie, and others.
This story and its links to The Thames Iron Works is to be continued…
