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Imperial standards of length

Imperial standards of length

The north east corner of Trafalgar Square

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Yards, feet and inches
Imperial standards of length

Standards of length were once represented by the distance between two marks on a solid metal bar. Copies of these standards were displayed in public places so that people could check the accuracy of the rules they were using. You can see an example set into the stone in Trafalgar Square between the statues of George IV and Admiral Beatty.

Increasing precision and standardisation
It was in 1308 that Edward I defined the inch as the length of three grains of barley, dry and round, taken from the middle of the ear. This standard enabled anyone to obtain an inch with sufficient accuracy for the times.
Notice about standards of length

Twelve inches make on foot. One yard is three feet, which is a normal single-arm stretch and measuring step. Elizabeth I defined our statute mile at 5280 feet.
In 1758, parliament set up a committee ?o inquire into the original standards of weights and measures of this kingdom? In 1762, the instrument maker, John Bird of London, constructed the yard rule which, by the Parliamentary Act of 1824, became the Imperial Standard Yard.
Note the importance of temperature The primary standards of weight and length in England were preserved at Westminster. These standards were destroyed when the Houses of Parliament burned down in 1834 and new primary standards had to be prepared.

Submitted by: Andrew Hunt, 16 January 2007

See the web site of the National Physical Laboratory for more information about the measurement of length and the definition of modern standards based on the metre.
A dictionary of units includes conversion factors from imperial to metric units with historical notes on measures generally and the conversion from imperial to metric units in the UK
Find out more about Trafalgar Square from
There are people campaigning to retain imperial units as you can see if you visit e this web sit.

See also: History of science

Project sponsors:

City sponsors:
ASE London Region
Nuffiled Curriculum Centre