Diving bell model. A glass bell with a brass fitting on top out of which a rubber tube projects. A length of string is tied to the fitting. Inside the bell is a rubber ring by the opening, suspended by wire from the top of the bell.

ABDNP:200063a

"Halley’s Diving Bell The diving bell made its appearance in the 16th century, under the name campana urinatoria, and accounts can be found of its use in the 17th century to recover sunken treasure. One adventure raised gold, chains and other articles from an Armada wreck off Mull. The most successful design of the early bells was that of Dr Edmund Halley (1656-1742); our model was made to show some of the principles he used. The original Halley ‘bell’ was a slightly conical chamber of 60 cubic feet with a flat glass roof and lead- coated wooden walls. Two divers sat in ordinary clothes on the circular seat within. Enough lead weights were secured to the bottom so that the whole could be lowered to the seabed, with pauses every 12 feet to allow the divers to adapt to the increasing pressure. The water rose up inside the bell as it was lowered but additional air was added from separate lead-covered casks with feeder tubes, lowered outside the bell from the ship above. By this means almost all the water could be expelled from the bell, allowing the divers to operate in almost dry conditions. Warm stale air was expelled from an orifice at the bell top. A diver could communicate by sending up a message with the used casks, written by an iron point on a lead pad. Halley’s bell worked in typical depths of 20 to 60 feet. It was susceptible to being tipped over if its edges caught on an obstruction while it was being lowered, with disastrous consequences for the divers. Diving technology has fortunately developed considerably in the ensuing 300 years. Our model is believed to be the late eighteenth-century demonstration piece recorded in Professor Patrick Copland’s inventory as ‘Diving bell, small glass model £0-2-6’. In the demonstration, the tube at the top was used for adding compressed air when it was underwater, rather than removing stale air as in the original bell."

Author: Reid,John.S Date: 1993 Purpose: University.Newsletter

1780-1800

glass, brass, rubber, string, iron wire
height 178 mm, diameter 105 mm

Physical Object