Diagram illustrating Hooke's invention for sounding the sea without a long line, using instead a ball sunk to the bottom of the sea by a weight which is released as soon as it touches the sea-floor and returns to the surface.
The design was was discussed at the meeting of the Royal Society on 30 September 1663, and printed in Philosophical Transactions, vol. 1 no. 9 (February 1666) and again in vol. 2 no. 24 (April 1667).