Origins
Historically, tonnage was the tax on tuns (casks) of wine that held approximately 252 gallons of wine and weighed approximately 2,240 pounds. This suggests that the unit of weight measurement, long tons (also 2,240 lb) and tonnage both share the same etymology. The confusion between weight based terms (deadweight and displacement) stems from this common source and the eventual decision to assess dues based on a ship's deadweight rather than counting the tuns of wine. In 1720 the Builder's Old Measurement Rule was adopted to estimate deadweight from the length of keel and maximum breadth or beam of a ship. This overly simplistic system was replaced by the Moorsom System in 1854 and calculated internal volume, not weight. This system evolved into the current set of internationally accepted rules and regulations.
When steamships came into being, they could carry less cargo, size for size, than sailing ships. As well as spaces taken up by boilers and steam engines, steamships carried extra fresh water for the boilers as well as coal for the engines. Thus, to move the same volume of cargo as a sailing ship, a steamship would be considerably larger than a sailing ship.
"Harbour Dues" are based on tonnage. In order to prevent steamships operating at a disadvantage, various tonnage calculations were established to minimise the disadvantage that the extra space requirements of steamships presented. Rather than charging by length or displacement etc., charges were calculated on the viable cargo space. As commercial cargo sailing ships are now largely extinct, Gross Tonnage is becoming the universal method of calculating ships dues, and is also a more straightforward and transparent method of assessment.
Read more about this topic: Tonnage
Famous quotes containing the word origins:
“Compare the history of the novel to that of rock ‘n’ roll. Both started out a minority taste, became a mass taste, and then splintered into several subgenres. Both have been the typical cultural expressions of classes and epochs. Both started out aggressively fighting for their share of attention, novels attacking the drama, the tract, and the poem, rock attacking jazz and pop and rolling over classical music.”
—W. T. Lhamon, U.S. educator, critic. “Material Differences,” Deliberate Speed: The Origins of a Cultural Style in the American 1950s, Smithsonian (1990)
“The settlement of America had its origins in the unsettlement of Europe. America came into existence when the European was already so distant from the ancient ideas and ways of his birthplace that the whole span of the Atlantic did not widen the gulf.”
—Lewis Mumford (1895–1990)
“Lucretius
Sings his great theory of natural origins and of wise conduct; Plato
smiling carves dreams, bright cells
Of incorruptible wax to hive the Greek honey.”
—Robinson Jeffers (1887–1962)