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British tower system of mass/weight

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Wikipedia.png This page uses content from the English Wikipedia. The original article was at Pound (mass)#Tower pound. The list of authors can be seen in the page history. As with the Units of Measurement Wiki, the text of Wikipedia is available under Creative Commons License see Wikia:Licensing.


The Pound

The Tower Pound

The system called tower weight was the more general name for King Offa's pound. This dates to 757 AD and was based on the silver penny. This in turn was struck over Arabic dirhams (2d). The pound was based on the weight of 120 Arabic silver dirhams, which have been found in Offa's Dyke. The same coin weight was used throughout the Hanseatic League.

The tower system was referenced to a standard prototype found in the Tower of London and ran concurrently with the avoirdupois and troy systems, until it fell out of use and was abolished in 1527.

Relationship between London and tower weightsEdit

1 London pound = 1⅓ tower pounds = 7,200 troy grains
¾ London pound = 1 tower pound = 5,400 troy grains
1 London ounce = 1 tower ounce = 450 troy grains
1 London pennyweight = 1 tower pennyweight = 22½ troy grains

Relationship between merchants' and tower weightsEdit

1 mercantile pound (15 oz) = 9,600 tower grains = 6,750 troy grains
1 tower pound (12 oz) = 7,680 tower grains = 5,400 troy grains
1 tower ounce (20 dwt) = 640 tower grains = 450 troy grains
1 tower pennyweight (dwt) = 32 tower grains = 22½ troy grains

Comparison of different English pounds

English pounds
Unit Pounds Ounces Grains Metric
metric Lond. avdp. merc. troy tower troy tower avdp. troy tower g kg
Metric 1 15/14 11/10 8/7 4/3 10/7 ≈ 16 ≈ 171/7 ≈ 173/5 ≈ 7716 ≈ 10974 500 1/2
London 14/15 1 36/35 16/15 5/4 4/3 15 16 1616/35 7200 10240 ≈ 467 7/15
Avoirdupois 10/11 35/36 1 28/27 175/144 35/27 147/12 155/9 16 7000 99555/9 ≈ 454 9/20
Merchant 7/8 15/16 27/28 1 75/64 5/4 141/16 15 153/7 6750 9600 ≈ 437 7/16
Troy 3/4 4/5 144/175 64/75 1 16/15 12 124/5 1329/175 5760 8192 ≈ 373 3/8
Tower 7/10 3/4 27/35 4/5 15/16 1 111/4 12 1212/35 5400 7680 ≈ 350 7/20


ReferencesEdit

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