Halley's diving bell, early 18th century.
© Science Museum / Science & Society Picture Library
Model. Edmond Halley (1656-1742) and others designed improvements to the diving bell in the early 18th century, as salvaging wrecks was profitable. The diving bell has a lens at the top for added light. Halley developed a system whereby air was lowered to the occupant of the diving bell in barrels, and used air was let out of the bell via a stopcock. This meant that divers could stay underwater for much longer than if they had to rely exclusively on the air that was in the diving bell when it first submerged. This tinplate model bell is asociated with Dr Stephen Demainbray (1710-1782), a science lecturer of the 18th century.