Chain (unit) facts for kids
A chain is a special unit used to measure length. It's part of the Imperial system, which is used in countries like the United Kingdom, and also in the United States. People mostly used chains to measure land. The short way to write "chain" is ch.
There are a few different kinds of chains, but the most common one is 66 feet long. That's about 20 metres. This common chain is also known as a surveyor's chain or land chain.
How Chains Were Used
The idea of the chain as a measurement came from how people measured acres of land. An acre was a certain length (a furlong) and a certain width (an "acre's breadth"). This "acre's breadth" was the original chain.
A smart person named Edmund Gunter created a real measuring tool called a chain. This chain was 66 ft (20 m) long. It was made of 100 small metal links. These links were thick wires with loops at each end. They were connected by three rings. The chain had brass handles at each end. People could fold it up and carry it easily. This is where the name chain for the unit came from!
The chain was very important in daily life in the United Kingdom and its colonies, and also in the United States. People used it to make maps and plan out new cities and towns. Land was surveyed (measured carefully) using these chains. Even when newer, more accurate ways of measuring came along, many people kept using the chain. This was because so much land had already been measured this way for a long time.
Today, chains are still used in some places. In the United Kingdom, railway lines are often measured in miles and chains. Farmers in the United States and Canada sometimes use special measuring wheels that are one-tenth of a chain around. Also, the length of a cricket pitch (the middle part of a cricket field) is exactly one chain.
Gunter's Chain
The Gunter's chain is the most common and standard type of chain. It is 66 feet long.
Ramsden's Chain
Sometimes, American surveyors used a longer chain. This one was 100 feet (about 30.48 meters) long. It's called the engineer's chain or Ramsden's chain. Instead of using fractions, this chain divided feet into decimals.
Hispanic Chain
In Texas, there was another type of chain used for measuring Spanish land grants. This chain is called the Hispanic chain or vara chain. It was based on a Spanish unit called the vara. A vara was similar to a yard in the old Spanish and Portuguese measuring systems.
One vara chain was equal to 20 varas. This was also about 60 Mexican feet, or roughly 55.5 English feet (about 16.9 meters).
See also
In Spanish: Cadena (unidad de longitud) para niños
