Acre

Irish measure or plantation measure was a system of units of land measurement used in Ireland from the 16th century plantations until the 19th century, with residual use into the 20th century. The units were based on "English measure" but used a linear perch measuring as opposed to the English rod of . Thus, linear units such as the furlong and mile, which were defined in terms of perches, were longer by a factor of 14:11 (~27% more) in Irish measure, while units of area, such as the rood or acre, were larger by 196:121 (~62% more). The Weights and Measures Act 1824 mandated the use throughout the British Empire of "Imperial measure", also called "statute measure", based on English measure. Imperial measure soon replaced Irish measure in the use of the Dublin Castle administration, but Irish measure persisted in local government, and longer still in private use. History The size of the mile and acre are derived from the length of the surveyor's rod, a unit which in Ireland was called a perch (or linear perch to distinguish it from the square perch). A mile is 320 linear perches and an acre is 160 square perches. The length of the perch was not standardised nationwide at the time of the Tudor conquest of Ireland; the city walls of Cork used a 29-foot perch. The 21-foot perch which became standard in Ireland during the Plantations was found elsewhere; in 1820 it was reportedly used for linear measure in Guernsey, and for measuring fencing in Herefordshire and "labourer's work" in South Wales. English measure was sometimes used in the Kingdom of Ireland. The Plantation of Munster of the 1580s used the English acre. In 1642 the Adventurers' Act, to compensate those who funded the army that put down the 1641 rebellion with land confiscated from rebels, specified amounts in "English measure", but was quickly amended to "Plantation measure". The "mile line" of the 1652 Cromwellian settlement, prohibiting Catholics settling within a mile of the Connacht coast or River Shannon, was an English statute mile. A 1653 survey of lands of the Countess of Ormonde in County Kilkenny used statute acres, whereas the 1654–5 Civil Survey and 1655–6 Down Survey used plantation acres. Irish acres were used in the 1823–37 applotments made under the Composition for Tithes (Ireland) Act 1823.