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Chain (unit)

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A chain is a unit for measuring length. It is part of the Imperial, United States customary and Spanish systems. People usually used it for measuring land. The short way of writing chains is ch.

There are a number of different definitions of the chain, from 50 to 100 feet long. In the Imperial system, one chain is equal to 66 feet or 20.1168 metres. This is also called a Gunter's chain, surveyor's chain or land chain.

History and usage

The chain was originally called an "acre's breadth" because it was the width of a acre, while a furlong was the length.

The clergy Edmund Gunter created a measuring device called a chain. The chain was 66 ft (20 m) long. It was divided by 100 in small metal links. The links were made of thick wire with a loop at each end. The links were connected to each other by three rings. There were brass handles at each end. People folded the chain up, link by link, and carried it in their hand. The name chain comes from these devices.

The unit was once important in everyday life in United Kingdom and its colonies and in the United States. People used it when they made maps and planned out cities and towns. Land was surveyed and measured using these chains. Even after more accurate ways of measuring land were created, many people continued to use the chain as a unit because land had already been surveyed in this method for so long.

In the United Kingdom, it is still used in the transport sector. Railway lines were built and measured in miles and chains. Farmers in the United States and Canada still use measuring wheels 110 of a chain around the outside.

The length of a cricket pitch is one chain.

Gunter's chain

The Gunter's chain is the standard unit.

Standard length
International Foot Yard Chain Furlong Mile Metres
Chain 66 22 1 110 180 20.1168
Gunter's survey units
International Link Rod Chain Metres
Chain 100 4 1 20.1168

Ramsden's Chain

American surveyors sometimes used a longer chain of 100 feet (30.48 m). This is called the engineer's chain or Ramsden's chain. The feet are divided by decimals instead of fractions.

Hispanic chain

In Texas, there is another chain for measuring Spanish land grants. This chain is called the Hispanic chain or vara chain. It is based on the vara. A vara is the equivalent of one yard in the old Spanish and Portuguese system of measurement.

1 vara chain =20 varas
=60 Mexican feet
=55+59 English feet
=16.93 metres

Since in Texas one Mexican foot is defined as 2527 English feet.

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