The Maritime Museum's Graham Lewis with Ivan Rundle from Macsalvors in front of the 35-tonne diving bell. Courtesy National Maritime Museum Cornwall

The National Maritime Museum Cornwall has taken an unusual, and rather large, delivery: a rare 1920s diving bell.

Weighing 35 tonnes, the old fashioned piece of diving equipment was donated to the museum by Diving Heritage, who found it at a salvage yard. Now residing in the museum boat yard, it will go on show in the exhibition Under the Sea, opening in January 2008.

“When we found this fantastic piece from our diving past in a salvage yard we knew this was a once in a lifetime opportunity as we doubt there is another one left in existence,” said Iain McQuarrie of Diving Heritage.

“It had to be preserved for future generations as it may have eventually ended up being scrapped and lost forever.”

An illustration of diving from 1830. © Science Museum Picture Library

The bell is one of the earliest types of apparatus used for working or exploring underwater, consisting of a ballasted chamber suspended from cables, lowered into the water from a crane on a ship or dock. Air is fed in to the bell from hoses, and becomes pressurised.

It was built by S Pearson & Sons Ltd for the renowned manufacturers Siebe Gorman and was fitted with electric lamps and even a telephone, as well as seats and four portholes. Visitors will be able to walk in to the big chamber at the new exhibition about the world of diving.

“It was be no means an easy feat getting the diving bell in to the store and then off the lorry,” said Graham Lewis, the Museum’s Boat Collection Assistant.

“But, thankfully Macsalvors who undertook the transport of the bell were fantastic at manoeuvring through the boats in the yard, despite the size of the lorry. And then, using their crane, we were able to swing the bell into an accessible position. Needless to say, everyone kept their toes clear of the landing deck!”