mar. law. The capacity of a ship or vessel. 3. The duties paid on the tonnage of a ship or vessel are also called tonnage. 4. These duties are altogether abolished in relation. to American vessels by the act of May 31, 1830, s. 1, 4 Story’s Laws U. S. 2216. And by the second section of the same act, all tonnage duties on foreign vessels are abolished, provided the president of the, United States shall be satisfied that the discriminating or countervailing duties of such foreign nation, so far as they operate to the disadvantage. of the United States, have been abolished. 5. The constitution of the United States provides, art. 1, s. 10, n. 2, that no state shall, without the consent of congress, lay any duty on tonnage.