|
A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself (usually then called a caisson) that rises and falls. Locks are used to make a river more easily navigable, or to allow a canal to take a reasonably direct line across land that is not level. ==Pound lock== A ''pound lock'' is a type of lock that is used almost exclusively nowadays on canals and rivers. A pound lock has a chamber with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock. Pound locks were first used in medieval China during the Song Dynasty (960–1279 AD), having been pioneered by the government official and engineer Qiao Weiyue in 984.〔 pp 350-351〕 They replaced earlier double slipways that had caused trouble and are mentioned by the Chinese polymath Shen Kuo (1031–1095) in his book ''Dream Pool Essays'' (published in 1088),〔Needham, Volume 4, Part 3, 351-352.〕 and fully described in the Chinese historical text ''Song Shi'' (compiled in 1345):〔Needham, Volume 4, Part 3, 351.〕
The water level could differ by or at each lock and in the Grand Canal the level was raised in this way by .〔 In medieval Europe a sort of pound lock was built in 1373 at Vreeswijk, Netherlands.〔Needham, Volume 4, Part 3, 357.〕 This pound lock serviced many ships at once in a large basin. Yet the first true pound lock was built in 1396 at Damme near Bruges, Belgium.〔 A famous civil engineer of pound locks in Europe was the Italian Bertola da Novate (c. 1410–1475), who constructed 18 of them on the Naviglio di Bereguardo (part of the Milan canal system sponsored by Francesco Sforza) between the years 1452 and 1458.〔Needham, Volume 4, Part 3, 358.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lock (water transport)」の詳細全文を読む スポンサード リンク
|