Sounding machines are used to determine the depth of water below a ship. This early 19th-century model is made of brass. It has a rotor which drives a pair of counters (one on each face) as it is dropped through the water on a rope. The device automatically locks when it touches the sea bed and can be then pulled to the surface and the final measurement recorded. The counter on the front is marked ‘0-10’, the one on the back ‘0-150’ (fathoms). This sounding machine was patented by Edward Massey (about 1768-1852), whose name is inscribed on the machine, along with the trademark of three Ls in a triangle.