SWEEPS. Large oars used on board ships of war in a calm, either to assist the rudder in turning them round, or to propel them ahead when chasing in light winds. Brigs of 386 tons have been swept at 3 knots or more.
(see Boatswain's Mate & Call above.)

On French vessels sweepers were the chiourme. Looks like “choir” but traces back to the Latin celeusma. In Southern France they were likely “galley slaves.” The Atlantic side not so much.