And be it furthered enacted, That an addition of ten per centum shall be made to the several rates of duties specified and imposed, in respect to all goods, wares and merchandise, which, after the said last day of December next, shall be imported in ships or vessels not of the United States, except in the cases in which an additional duty is herein before specially laid on any goods, wares, or merchandises, which shall be imported in such ships or vessels.
32.
The court noted that the original meaning of the clause was as a term of art for a tax imposed that varies with " the internal cubic capacity of a vessel, " but emphasized that a consistent line of cases had read the clause broadly, " forbidding a State to do that indirectly which she is forbidden . . . to do directly . " Those cases, the court concluded, stood for the proposition that the tonnage clause's prohibition reaches any taxes or duties on a ship, " whether a fixed sum upon its whole tonnage, or a sum to be ascertained by comparing the amount of tonnage with the rate of duty [, ] . . . regardless of [ the tax or duty's ] name or form . . . which operate to impose a charge for the privilege of entering, trading in, or lying in a port .
