Evening star., 1943-04-30
Ship Tonnage Dispute
Grows Out Of VARYING
Computation Methods
Worships Measured by
Displacement, Merchant
Vessels Usually by Gross
BY the Associated Press.

BY the Associated Press.
How much is ton of ship?
Even the experts occasionally
stumble on the answer to that one,
as demonstrated this week in the
dispute between the Truman com.
mittee and Secretary Knox over the
tonnage of Allied shipping lost and
built last year.
A pertinent point, it develops, is
the formula used in determining the
various tonnage figures involved.
And that, congressional experts said
today, makes lot of difference.
To begin with, a ton" OF war
ship and ton" of merchant ship,
either cargo or passenger, are en-
tirely different things.
Displacement Measures Warship.
Warships are measured in dis
placement" tons, which means the
actual weight of the vessel, includ-
ing hull and machinery, arms,
armor and ammunition, with ships
stores and personnel aboard and
ready to 60 to sea except for water
in the boilers and fuel oil.
Vessels thus equipped are weigh
ed" by the volume of water dis
placed, under the principle discov-
cred $500 years ago by the Greek
scientist Archimedes, that a floating
body displaces volume OF water
equal to its own weight.
On the other hand, a ton" Of
merchant ship is unit OF measure
ment Of the vessels carrying capac-
tty, arrived at by several different
methods Of computatio and, except
when expressly referring to dis
placement, has no connection with
the weight Of the ship itself.
Several Merchantman figures.
The most frequently used tonnage
figures for merchant vessels are
gross. dead weight and registered,
or net.
Gross tonnage Is the figure usually
employed, and it is this type of ton
mage generally referred to in figures
on sinkings.
Gross tonnage Is the capacity or
volume Of the inclosed area Of
ship expressed in terms of one ton
for every 100 cubic feet of space, a
standard adopted by both United
States and British navigation laws.
The 100-cubic- -feet-p -per-ton formula
Is applied regardless Of the type of
cargo actually carried.
Dead-weight tonnage, on the other
hand, Is the weight in tons of
ships cargo, passengers, crew, fuel
and stores which can be carried
when fully loaded, and is measured
by the difference in displacement of
the vessel when light and when
loaded. Dead-weight tonnage is the
figure usually employed in construc-
ton statistics.
Loading Limit Marked.
The loading limit of a merchant
ship is marked by the load line. or
plimsoll mark, painted on the hull
The other common formula for
measuring tonnage, registered" or
met" represents the gross tonnage
less the space taken up by propelling
machinery, crews quarters, and
other necessary purposes which rep
resent no earning power. 1t is this
figure which is used for registration
or Recommendation under the naviga-
ton laws:
Thus the wide variations in the
dlf1erent tonnages of a particular
ship may easily be understood. A
cargo ship with a nominal dead
weight tonnage Of about 5000 tons
might have a displacement" of
perhaps 10000 tons, a gross tonnage
OF 5000 and registered tonnage
Of 1000.
Ship tonnage measurement has for
ITS two principal purposes estab-
hshment OF a basis for payment of
various port and harbor charges
and pilotage fees and canal tolls, and
to provide a ready system of regis
tration and Identification