Sounding machines measure the depth of water beneath a ship. The sounder is attached to a rope and lowered off the side. As it sinks through the water the vane rotates, turning the attached wormscrew below, which engages with and turns the counter. When it hits the seabed, the machine locks and it can be hauled back up for the depth measurement to be read off the counter. This design was patented by Edward Massey in 1802.

Sounding machines measure the depth of water beneath a ship. The sounder is attached to a rope and lowered off the side. As it sinks through the water the vane rotates, turning the attached wormscrew below, which engages with and turns the counter. When it hits the seabed, the machine locks and it can be hauled back up for the depth measurement to be read off the counter. This design was patented by Edward Massey in 1802.