Spalding's diving bell. Historical illustration of Spalding's diving bell in action. The bell consisted of a lead-covered truncated wooden cone, 2.4 metres in height. It is seen (bottom centre) being lowered from a rowing boat next to the sailing ship. The two small barrels are raised and lowered alternately to supply fresh air. One of these is seen renewing the bell's air supply. Illustration from a book published in 1815.