Yard

A yard is a unit of length used in the British imperial and US customary systems. It is defined as being equal to 3 feet or 36 inches.

This measurement is vital for organizing trade and land use. For example, a distance of 1,760 yards is equal to one mile. Since 1959, an international agreement has standardized the yard. It is now defined as exactly 0.9144 meters. This ensures that measurements remain consistent across different countries.

Historically, the yard functioned as a line standard. This means the length was defined by a physical object. One official British standard was a straight brass rod. This rod had gold plugs installed in recesses near each end. The yard was the distance between the centers of these two gold plugs.

Because metal changes size with temperature, the measurement was specific to a certain heat. The distance was only considered a true yard at 62 degrees Fahrenheit. This precision prevented errors caused by the expansion or contraction of the metal.

There are several different ways the yard has been defined over time. In early English history, it was often linked to the "ell." An ell was a separate unit of length, usually around 45 inches. The term "yard" itself likely comes from Old English words for branches or measuring rods. In some contexts, it was also used as a unit of land assessment called a yardland. In India, a similar three-foot measure is colloquially known as a guz. These variations show how different cultures developed their own ways to quantify space.

The exact origins of the yard remain a subject of debate among historians. Some believe it derived from the "cubit," which is an arm's-length. Others suggest it came from the "pace," or the distance of a step. During the reign of Henry I, from 1100 to 1135, the king used his own arm as a standard. He did this to correct the "false ell" used by traders. There is even a folktale claiming the length was bounded by a king's nose. While some historians call this account childish, it shows how central physical standards were to authority.

Measurement laws were often created to ensure fairness in commerce. In 1439, a law was passed regarding the sale of cloth. Previously, merchants sold cloth by the "yard and handful." This allowed them to evade high taxes through unofficial extra amounts. The law replaced this with the "yard and inch" system. This change was sanctioned again in several acts between 1552 and 1558. These laws helped create a single, official measure of cloth throughout the realm.

Physical standards have faced many challenges, including destruction by fire. In 1834, a fire known as the Burning of Parliament destroyed the primary Imperial yard standard. To fix this, a commission was formed in 1838 to reconstruct the lost measures. In 1845, a new standard was built using Baily's metal No. 4. This specific alloy consisted of 16 parts copper, 3 parts tin, and 1 part zinc. The new bar was 38 inches long and 1 inch square.

The distribution of these standards helped maintain accuracy across the globe. After the new standard was made, forty different yard standards were constructed. Four of these were called "parliamentary copies." They were sent to important places like the Royal Observatory at Greenwich and the Royal Mint. Other copies were sent to cities like London, Edinburgh, and Dublin. The United States also received an official imperial standard. This specific version is known as Bronze Yard No. 11.

This allowed the US to use a standard that matched the British system.