WEIR

barrier placed acro river to raise the water-level. Used for. mill races. and purposes of navigation. Saxons used arrangements of stakes and twigs as fish traps and water dams. When water wheels were a source of power w.’s were used to divert the current to the wheel. W.’s are generally of three types; solid, watertight dams of earthwork, simple, strong, and durable; draw do or, by which the discharge of the river may be regulated by sluice gates; and movable, consisting of iron frames in beds of masonry.