(1) If any ship carries as deck cargo, that is to say, in any uncovered space upon deck, or in any covered space not included in the cubical contents forming the ship's registered tonnage, timber, stores or other goods, all dues payable on the ship's tonnage shall be payable as if there were added to the ship's registered tonnage the tonnage of the space occupied by those goods at the time at which the dues become payable.

(2) The space so occupied shall be deemed to be the space limited by the area occupied by the goods and by straight lines enclosing a rectangular space sufficient to include the goods.