2. The cubical content or burden of a vessel, or vessels, in
tons; or, the amount of weight which one or several
vessels may carry. See {Ton}, n.
(b) .
A fleet . . . with an aggregate tonnage of
60,000 seemed sufficient to conquer the world.
--Motley.
3. A duty or impost on vessels, estimated per ton, or, a
duty, toll, or rate payable on goods per ton transported
on canals.
4. The whole amount of shipping estimated by tons; as, the
tonnage of the United States. See {Ton}.
Note: There are in common use the following terms relating to
tonnage: (a) Displacement. (b) Register tonnage, gross
and net. (c) Freight tonnage. (d) Builders'
measurement. (e) Yacht measurement. The first is mainly
used for war vessels, where the total weight is likely
to be nearly constant. The second is the most
important, being that used for commercial purposes. The
third and fourth are different rules for ascertaining
the actual burden-carrying power of a vessel, and the
fifth is for the proper classification of pleasure
craft. Gross tonnage expresses the total cubical
interior of a vessel; net tonnage, the cubical space
actually available for freight-carrying purposes. Rules
for ascertaining these measurements are established by
law.