AskDefine | Define burthen

Dictionary Definition

burthen n : a variant of `burden' v : weight down with a load [syn: burden, weight, weight down] [ant: unburden]

User Contributed Dictionary

English

Pronunciation

Noun

  1. the tonnage of a ship based on the number of tuns of wine that she could carry in her holds.
  2. an archaic variant of burden.

Quotations

* 1883: Robert Louis Stevenson, Treasure Island
  • The other men were variously burthened; some carrying picks and shovels - for that had been the very first necessary they brought ashore from the Hispaniola - others laden with pork, bread, and brandy for the midday meal.*1798, William Wordsworth, Lines composed a few miles above Tintern Abbey, lines 36-43 (for syntax)
    Nor less, I trust,
    To them I may have owed another gift,
    Of aspect more sublime; that blessed mood,
    In which the burthen of the mystery,
    In which the heavy and the weary weight
    Of all this unintelligible world,
    Is lightened:
  • 1817: Jane Austen, ''Persuasion
    It was with a daughter of Mr Shepherd, who had returned, after an unprosperous marriage, to her father's house, with the additional burthen of two children.

Extensive Definition

Builder's Old Measurement (BOM) is the method of calculating the size or cargo capacity of a ship used in England from approximately 1720 to 1849. The BOM estimated the tonnage of a ship based on length and maximum beam. The formula is:
= \frac where:
  • Length is the length, in feet, from the stem to the sternpost;
  • Beam is the maximum beam, in feet.
Thus, BOM estimates the weight of the cargo carrying capacity of a ship measured in tons, a weight that is also termed deadweight. The Builder's Old Measurement formula remained in effect until the advent of steam propulsion. Steamships required a different method of measuring tonnage, because the ratio of length to beam was larger and a significant volume of internal space was used for boilers and machinery. In 1849 the Moorsom System was created in Great Britain. Instead of calculating deadweight, the Moorsom system calculates the cargo carrying capacity in cubic feet, a volumetric measurement rather than a weight measurement. The capacity in cubic feet is then divided by 100 cubic feet of capacity per gross ton, resulting in a tonnage expressed in tons.

History and Derivation

The first tax on the hire of ships in England was levied by King Edward I in 1303 based on tons of burthen (burden). Later, King Edward III levied a tax of 3 shillings on each "tun" of imported wine. At that time a "tun" was a wine container of 252 gallons weighing about 2240 lbs. In order to estimate the capacity of a ship for tax purposes, an early formula used in England was
= \frac
where:
    • Length is the length (undefined), in feet
    • Beam is the beam, in feet.
    • Depth is the depth of the hold, in feet below the main deck.
    • 100 the divisor is undefined, but the units would be ft³ per tun
Or by solving : = \frac
In 1694 a new British law required that tonnage for tax purposes be calculated according to a similar formula:
= \frac
This formula remained in effect in until the Builders Old Measurement rule was put into use in 1720, and then by Parliamentary law in 1773.

References

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