In 1775, Pennsylvania Magazine wanted its readers to be up to date on the very latest in technological advances, including this machine for… well, it seems to be some kind of a caisson for dredging harbors, more than something that “cleanses docks.” Anyway, it’s very impressive, this American ingenuity.
From the device’s description: The machine consists of a horse-drawn crane on a boat with a crane and shovel. A man is shown operating the shovel. Includes a detail of the construction of the crane tower.
Found in Brown University’s JCB Collection, which is full of early American imagery.