Editing Lock (water navigation) (section)

==Pound lock==
[[File:Keiteleen kanava.jpg|thumb|A pound lock on the Keitele–[[Päijänne]] Canal at [[Äänekoski]] in [[Central Finland]]]]

A ''pound lock'' is most commonly used on [[canal]]s and [[river]]s today.<ref>{{Cite news|url=https://www.popularmechanics.com/technology/infrastructure/g2875/7-impressive-boat-locks/|title=7 of the World's Most Impressive Canal Locks|last=Newcomb|first=Tim|date=13 December 2016|work=Popular Mechanics}}</ref> A pound lock has a chamber with [[floodgate|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]].<ref name="needham volume 4 part 3 352">{{Cite book|first1=Joseph|last1=Needham|first2=Gwei-Djen|last2=Lu|first3=Ling|last3=Wang|title=[[Science and Civilisation in China]]|section=Civil Engineering and Nautics|volume=4:3|publisher=Cambridge University Press|location=Cambridge|year=1971|pages=352}}</ref>

Pound locks were first used in China during the [[Song dynasty]] (960–1279 CE), having been pioneered by the Song politician and naval engineer [[Technology of the Song dynasty#Civil engineering|Qiao Weiyue]] in 984.<ref name="needham volume 4 part 3 350 351">Needham, Volume 4, Part 3, 350-351.</ref> They replaced earlier double [[slipway]]s that had caused trouble and are mentioned by the Chinese [[polymath]] [[Shen Kuo]] (1031–1095) in his book ''[[Dream Pool Essays]]'' (published in 1088),<ref name="needham volume 4 part 3 351 352">Needham, Volume 4, Part 3, 351–52.</ref> and fully described in the [[Twenty-Four Histories|Chinese historical text]] ''Song Shi'' (compiled in 1345):<ref name="needham volume 4 part 3 351">Needham, Volume 4, Part 3, 351.</ref>
<blockquote>
The distance between the two locks was rather more than 50 paces, and the whole space was covered with a great roof like a shed. The gates were 'hanging gates'; when they were closed the water accumulated like a tide until the required level was reached, and then when the time came it was allowed to flow out.
</blockquote>

The water level could differ by {{convert|4|or|5|ft|m}} at each lock and in the [[Grand Canal (China)|Grand Canal]] the level was raised in this way by {{convert|138|ft|m}}.<ref name="needham volume 4 part 3 351"/>

In medieval Europe a sort of pound lock was built in 1373 at [[Vreeswijk]], Netherlands.<ref name="needham volume 4 part 3 357">Needham, Volume 4, Part 3, 357.</ref> This pound lock serviced many ships at once in a large [[Basin (maritime)|basin]]. Yet the first true pound lock was built in 1396 at [[Damme]] near [[Bruges]], Belgium.<ref name="needham volume 4 part 3 357"/> The [[Italy|Italian]] Bertola da Novate (c. 1410–1475) constructed 18 pound locks on the [[Naviglio di Bereguardo]] (part of the [[Milan]] canal system sponsored by [[Francesco Sforza]]) between 1452 and 1458.<ref name="needham volume 4 part 3 358">Needham, Volume 4, Part 3, 358.</ref>

In Ancient Egypt, the river-locks was probably part of the [[Canal of the Pharaohs]]: Ptolemy II is credited by some{{who|date=May 2024}} for being the first to solve the problem of keeping the Nile free of salt water when his engineers invented the lock around 274/273 BC.<ref>{{cite book| last = Gmirkin| first = Russell E.| title = Berossus and Genesis, Manetho and Exodus: Hellenistic Histories and the Date of the Pentateuch| publisher = Bloomsbury 3PL| date = 2006| page = 236| isbn = 978-0567025920 }}</ref>