A Giant That Looked Like a Half Pipe
In the 1860s London engineers built a floating dry dock so large that its U shaped walls reminded later viewers of a gigantic half pipe. The structure was created for Bermuda, where porous limestone made a normal dry dock impossible. By 1866 the plan was set.
The dock would lift warships out of the water, hold them steady for repairs, and even turn itself on its side so workers could clear marine growth. It displaced about 8400 tons and relied on internal compartments that could flood and empty to raise or lower the massive iron frame.
Built on the Thames and Launched Sideways
Construction took place at the Campbell and Johnstone yard on the River Thames. About 1400 workers hammered plates and rivets. In September 1868 the huge iron cradle was launched sideways into the river. Through the winter it waited at Sheerness near the mouth of the Thames until weather conditions allowed the journey to begin. The tow would start in June 1869.
There were no ocean tugs designed for such a task, so two large ironclad warships, Agincourt and Northumberland, pulled the dock from Britain to Madeira. From Madeira the tow changed hands to Warrior and Black Prince, while the paddle frigate Terrible guided from behind. Sailcloth was stretched between the high iron walls, and easterly winds helped push the structure westward.
Five Knots Across the Atlantic and Into Bermuda
The floating dock moved at an average of just under five knots, about five point seven miles per hour, and at times reached six knots. On 28 July 1869 locals in Bermuda saw two grey hulks towing a long iron box toward Hamilton. People watched from hilltops and crowded small boats. The final approach required passage through The Narrows, a narrow channel between reefs.
The large ironclads could not take the dock through, so Terrible and the local tug Spitfire led. Gunboats Viper, Vixen, and Lapwing made fast alongside to help steer. Mooring ropes snapped more than once, tides forced delays, and a sudden squall twisted the dock at a risky point in the channel. Terrible steadied the tow and brought it into calmer water. At Grassy Bay the prepared moorings dropped to the bottom, so the crew used anchors to hold the dock in place. On 31 July 1869 valves were opened so the dock settled safely on the seabed.
Thirty Years of Work in Bermuda
Once moved into the Camber, the deep water shelter at the dockyard, the enormous iron frame began its service life. It lifted damaged warships out of the sea, took on wooden paddle frigates, and rolled gently to one side to allow cleaning. It measured 381 feet long, 74 feet tall, and 123 feet at its widest point. For more than thirty years it served the North America and West Indies Station.
In 1902 a newer steel built Admiralty Floating Dock Number One arrived. The old dock was sold for scrap to a German firm. While under tow it parted its towlines and grounded near Stovell Bay at Spanish Point. Attempts to break it apart with explosives did not remove it entirely, and remains of the nineteenth century dock are still visible in Bermuda.
In 1869 a giant U shaped iron floating dock crossed the Atlantic to Bermuda, towed by warships and steadied by a paddle frigate.
Built for an island where porous limestone stopped dry docks, it faced reefs, squalls, and tight channels before it could begin work…🧵👇 pic.twitter.com/50EZ6CaoYf
— Fascinating True Stories (@FascinatingTrue) November 11, 2025