a quantity of stones, gravel, or sand, laid in a ship's hold, to make her sink to a certain depth into the water, and fail upright. The ballast is sometimes one quarter, one third, or one half, according to the difference of the bulk of the ship. Flat vessels require the most ballast. Ships are said to be in ballast, when they have no other loading. Masters of vessels are obliged to declare the quantity of ballast they bear, and to unload it at certain places. They are prohibited unloading their ballast in havens, roads, &c., the neglect of which has ruined many excellent ports.