An acre is a measure of ground approximately adopted by most nations, which in America and England is 4,840 square yards. The chain with which land is measured is 22 yards long, and a square chain will contain 22x22, or 484 yards; so that 10 square chains make an acre. The acre is divided into 4 roods, a rood into 40 perches, and a perch contains 301/4 square yards. The old Scotch acre is larger than the English, and the Irish than the Scotch. Twenty-three Scotch acres = 29 imperial acres; 301/4 Irish acres = 49 imperial acres. The hectare of the French metric system has on the Continent superseded almost all the ancient local measures corresponding to the acre - such as the Prussian morgen.