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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. [4] Pound locks were first used in China during the Song dynasty (960–1279 CE), having been pioneered by the Song politician and naval engineer Qiao Weiyue in 984. [5]
A short pound on the Chesterfield Canal in England, United Kingdom. A canal pound (from impound), [1] reach, or level (American usage), is the stretch of level water impounded between two canal locks. Canal pounds can vary in length from the non-existent, where two or more immediately adjacent locks form a lock staircase, to many kilometres/miles.
The Pound–Drever–Hall (PDH) technique is a widely used and powerful approach for stabilizing the frequency of light emitted by a laser by means of locking to a stable cavity. The PDH technique has a broad range of applications including interferometric gravitational wave detectors , atomic physics , and time measurement standards , many of ...
All three sets of locks are paired; that is, there are two parallel flights of locks at each of the three lock sites. This, in principle, allows ships to pass in opposite directions simultaneously; however, large ships cannot cross safely at speed in the Culebra Cut, so in practice ships pass in one direction for a time, then in the other ...
Pound was the Mallinckrodt Professor of Physics emeritus at Harvard University. [4] He was a member of the class of 1941 at the University at Buffalo. [4] Pound's name is also attached to the Pound–Drever–Hall technique used to lock the frequency of a laser on a stable optical cavity.
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The pound lock holds water between two gates, and is considerably easier to navigate. Pound locks have been built in China since 983, in the Netherlands from 1065 and in Britain from the 1560s. Nevertheless, a few flash locks remained after the introduction of pound locks.
Locks are popular visitor attractions, and many serve refreshments. Locks were often built adjacent to islands and therefore many are situated in remote locations, hard to find and can only be reached on foot. Many locks also have moorings that can be used overnight, and some include electric charging points for electric powered boats.