Diving Deep: HMS Invincible 1744 tells the story of Invincible from the time that she was captured from the French in 1747 to the latest excavation of the wreck site during 2016-2019. Our Family Learning & Outreach Coordinator, Linda Brown, remembers the day that she was fortunate enough to visit the HMS Invincible archaeological excavation site in the Solent, just off the coast from Portsmouth…
The visit began with an exhilarating (very bumpy and wet) ride in the RIB out to the dive barge, a large floating platform packed with various cranes, equipment and shipping containers providing shelter, storage and accommodation. The actual matter of getting onto the barge was quite a challenge, involving climbing up huge lorry tyres dangling from the rolling deck, however, it was certainly worth the effort.
Once onboard we were made welcome and given the opportunity to talk to the divers and support staff and watch, first-hand, the hard work involved in excavating below the waves. The equipment that the divers needed to wear and use was very heavy and because the deck was fairly high above the sea, there was a lift which lowered them into the water. In one of the containers onboard was a communication system that allowed the dive master to observe and monitor the work being carried out approximately 9 meters below. It was surprising just how clear the picture was on the screen and just how clear the verbal communication was. Unlike a dig on land the artefacts have to be uncovered carefully using a vacuum dredger to remove the sand and silt covering the site. A large drainage pipe was fitted with a pressurised air supply near to the lower end and the air rose through the tube forming a vacuum below it causing the sand to be sucked up and deposited elsewhere.
A mesh across the end prevented any artefacts being sucked up and lost. Much of the wreck was the wood from which HMS Invincible was built and we watched as a diver was hard at work using a pneumatic chainsaw to cut off slices of wood for dendrological examination. This was an exceedingly dangerous task since the diver needed to be aware of where his body, particularly his feet, were at all times as the currents moved him at will, often placing him in precarious positions during this particular operation.
The wreck was spread out over two main areas and although the visibility was good on the day we visited, it was not always like that. So, a very useful procedure to permit research at any time is photogrammetry. This is a series of thousands of photographs, stitched together to make a 3D view of the wreck making it possible to investigate the wreck site from land.
The artefacts which had been retrieved from the wreck site were stored on the deck in water until they could be sent to the appropriate laboratories for cleaning and conservation. Whilst we were visiting a bottle, similar to the one in the picture below, was brought to the surface. The best conditioned timbers and other items were those which had been buried under the mud and silt for 260 years, as they were anaerobically preserved, such as a lack of oxygen which prevented the ship worm and gribble from destroying the objects.
In the Diving Deep: HMS Invincible 1744 exhibition there is a particularly good example of this where a broom head, which was under the silt, is in almost original condition compared to the handle which was above the silt and has been badly eroded.
Why not pay a visit to Diving Deep HMS Invincible 1744 Exhibition at The Historic Dockyard Chatham and experience interactive displays and see the full exciting story of HMS Invincible for yourself, open from 12 February to 20 November 2022.
This blog was written by our Family Learning & Outreach Coordinator, Linda Brown.