Ships are generally larger than boats, but there is no universally accepted distinction between the two. Ships generally can remain at sea for longer periods of time than boats. A legal definition of ship from Indian case law is a vessel that carries goods by sea. A common notion is that a ship can carry a boat, but not "vice versa". A US Navy rule of thumb is that ships heel towards the "outside" of a sharp turn, whereas boats heel towards the "inside" because of the relative location of the center of mass versus the center of buoyancy. American and British 19th century maritime law distinguished "vessels" from other craft; ships and boats fall in one legal category, whereas open boats and rafts are not considered vessels.