Editing Lock (water navigation) (section)

==Details and terminology==
===Rise===
The ''rise'' is the change in water-level in the lock. The two deepest locks on the English canal system are [[Bath Locks|Bath deep lock]]<ref>{{cite web | title=Second Lock | work=Images of England | url=http://www.imagesofengland.org.uk/details/default.aspx?id=442716 | archive-url=https://web.archive.org/web/20071116175605/http://www.imagesofengland.org.uk/details/default.aspx?id=442716 | url-status=dead | archive-date=16 November 2007 | access-date=4 September 2006}}</ref><ref>{{cite book |last=Allsop |first=Niall |title=The Kennet & Avon Canal |year=1987 |publisher=Millstream Book |location=Bath |isbn=0-948975-15-6 |url-access=registration |url=https://archive.org/details/kennetavoncanalu0000alls }}</ref> on the [[Kennet and Avon Canal]] and [[Tuel Lane Lock]] on the [[Rochdale Canal]], which both have a rise of nearly {{convert|20|ft|m}}. Both locks are amalgamations of two separate locks, which were combined when the canals were restored to accommodate changes in road crossings. By comparison, the Carrapatelo and Valeira locks on the [[Douro]] river in Portugal, which are {{convert|279|ft|m}} long and {{convert|39|ft|m}} wide, have maximum lifts of {{convert|115|and|108|ft|m}} respectively.<ref>{{cite web|url=https://books.google.com/books?id=aAwvJ5HWPIcC&pg=PA297|title=Final Report of the International Commission for the Study of Locks|work=Google Books|access-date=20 May 2013}}</ref> 

The two [[Ardnacrusha power plant|Ardnacrusha]] locks near [[Limerick]] on the Shannon navigation in Ireland have a rise of {{convert|100|ft|m}}. The upper chamber rises {{convert|60|ft|m}} and is connected to the lower chamber by a tunnel, which when descending does not become visible until the chamber is nearly empty.<ref>{{cite web|url=http://irishwaterwayshistory.com/abandoned-or-little-used-irish-waterways/the-lower-shannon/shannon-south/the-esb-lock-at-ardnacrusha/|title=The ESB lock at Ardnacrusha |date=22 July 2009 |publisher=Irish Waterways History |access-date=2012-03-23}}</ref>

===Pound===
A ''[[Canal pound|pound]]'' is the level stretch of water between two locks (also known as a ''reach'').<ref>{{cite book |title=[[Oxford English Dictionary]] |year=1989 |publisher= Oxford University Press|location=Oxford, England|edition=Second |chapter=Reach |quote= ...the portion of a canal between two locks, having a uniform level}}</ref>

===Cill===
The ''cill'', also spelled ''sill'', is a narrow horizontal ledge protruding a short way into the chamber from below the upper gates. Allowing the rear of the boat to "hang" on the cill is the main danger when descending a lock, and the position of the forward edge of the cill is usually marked on the lock side by a white line. The edge of the cill is usually curved, protruding less in the center than at the edges. In some locks, there is a piece of oak about {{convert|9|in|cm|abbr=on}} thick which protects the solid part of the lock cill. On the Oxford Canal it is called a babbie; on the Grand Union Canal it is referred to as the cill bumper. Some canal operation authorities, primarily in the United States and Canada, call the ledge a ''miter sill'' (mitre sill in Canada).<ref name="MERRIAM">[http://www.merriam-webster.com/dictionary/miter%20sill Merriam-Webster Dictionary, definition of miter sill], Retrieved Jan. 28, 2015.</ref>
{{Anchor|Gates}}

==== Photo gallery ====
<gallery mode=packed>
File:Canal Saint-Denis-Ecluse N°1-Le petit bief.JPG|The cill exposed in the deep Pont de Flandre lock on the [[Canal Saint-Denis]], Paris
File:Eynsham Lock - geograph.org.uk - 5594146.jpg|The balance beams typical of many locks on the [[River Thames|Upper Thames]] at [[Eynsham Lock]], [[Eynsham]], [[Oxfordshire]], England. Visible on the gates are the paddle winding gears, used to operate the [[sluice|sluice gates]].
File:JesusGreenLock-Cambridge.jpg|Top gates of [[Jesus Lock]], a beam lock on the [[River Cam]] in [[Cambridge]], England
File:ZSchützmechanik.jpg|200-year-old paddle gear on the [[:de:Wiener Neustädter Kanal|Wiener Neustädter Kanal]], Austria
File:BCN water conservation lock.jpg|Water conservation gear on the [[Birmingham Canal Navigations]]
File:Lock gate cogs, Montgomery Canal - geograph.org.uk - 1806427.jpg|Lock gate controls on a [[canal]]
File:Caversham Lock - geograph.org.uk - 5907080.jpg|[[Caversham Lock]] on the River Thames, with its chamber nearly filled. Visible on top of the gates are the [[hydraulics|hydraulic mechanisms]] that raise and lower the sluices in their raised position. To the right is one of two pedestals which are used to operate the gates and sluices, as well as the lock cottage.
</gallery>

===Gates {{Anchor|Gates}}===
Gates are the watertight doors which seal off the chamber from the upper and lower pounds. Each end of the chamber is equipped with a gate, or pair of half-gates, traditionally made of [[oak]] or [[elm]] but now usually made of [[steel]]). The most common arrangement, usually called ''miter gates'', was invented by [[Leonardo da Vinci]] sometime around the late 15th century.<ref name="Encyclopedia.com 2018 u962">{{cite web |date=2018-05-17 |title=Canal Lock |url=https://www.encyclopedia.com/science-and-technology/technology/technology-terms-and-concepts/canal-lock |access-date=2023-08-13 |website=Encyclopedia.com}}</ref>

===Paddle===
On the old [[Erie Canal]], there was a danger of injury when operating the paddles: water, on reaching a certain position, would push the paddles with a force which could tear the windlass (or handle) out of one's hands, or if one was standing in the wrong place, could knock one into the canal, leading to injuries and drownings.<ref>{{cite book|last=Garrity|first=Richard|title=Canal Boatman My Life on Upstate Waterways|year=1977|publisher=Syracuse University Press|location=Syracuse, NY|isbn=0-8156-0139-5|page=38}}</ref>

=== Windlass ("lock key") ===
[[File:Lock Windlasses and Rakes on Chesapeake and Ohio Canal.JPG|thumb|upright|Collection of lock windlasses. Note: rakes are for clearing trash out of the lock.]]
On the Chesapeake and Ohio Canal, the lockkeepers were required to remove the windlasses from all lock paddles at night, to prevent unauthorized use.<ref>Unrau p. 336</ref>

===Swell or swelling===
A ''swell'' was caused by opening suddenly the paddle valves in the lock gates, or when emptying a lock.<ref name="Garrityswell">{{cite book|last=Garrity|first=Richard|title=Canal Boatman My Life on Upstate Waterways|year=1977|publisher=Syracuse University Press|location=Syracuse, NY|isbn=0-8156-0139-5|pages=39}}</ref>
To help boats traveling downstream exit a lock, the locksman would sometimes open the paddles to create a swell, which would help "flush" the boat out of the lock. A boatsman might ask for a back swell, that is, to open and shut the paddles a few times to create some waves, to help him get off the bank where he was stuck.<ref>Kytle, Elizabeth. ''Home on the Canal''. Seven Locks Press, 1983. p. 207</ref> If boats ran aground (from being overloaded) they sometimes asked passing crews to tell the upstream lock to give them an extra heavy swell, which consisted of opening all the paddles on the lock gate, creating a surge that affected the whole pound below.<ref>Garrity, Richard. p. 40</ref>

On the Erie Canal, some loaded boats needed a swell to get out of the lock. Particularly lumber boats, being top heavy, would list to one side and get stuck in the lock, and needed a swell to get them out. Some lockkeepers would give a swell to anyone to help them on the way, but some would ask for money for the swell.<ref name="Garrityswell"/>

The Erie Canal management did not like swelling for two reasons. First, it used too much water lowering the water on the pound above sometimes causing boats to run aground. In addition, it raised the water level on the pound below, causing some boats to strike bridges or get stuck.<ref name="Garrityswell"/>

===Snubbing posts===
[[File:Snubbing a boat C and O Canal 1.jpg|thumb|Snubbing a boat to keep it from hitting the downstream gates. Note the rope wrapped around the snubbing post.]]
On horse-drawn and mule-drawn canals, snubbing posts were used to slow or stop a boat in the lock. A 200-ton boat moving at a few miles an hour could destroy the lock gate. To prevent this, a rope was wound around the snubbing post as the boat entered the lock. Pulling on the rope slowed the boat, due to the friction of the rope against the post.<ref>Kytle, Elizabeth. ''Home on the Canal''. 1996. {{ISBN|0801853281}}, p. 133</ref> A rope {{convert|2+1/2|in|cm}} in diameter and about {{convert|60|ft|m|abbr=off|sp=us}} long was typically used on the Erie Canal to snub a boat in a lock.<ref>Garrity, Richard. p. 41</ref>

One incident, which took place in June 1873 on the Chesapeake and Ohio Canal, involved the boat the ''Henry C. Flagg'' and its drunk captain. That boat was already leaking; the crew, having partially pumped the water out, entered Lock 74, moving in front of another boat. Because they failed to snub the boat, it crashed into and knocked out the downstream gates. The outrush of water from the lock caused the upstream gates to slam shut, breaking them also, and sending a cascade of water over the boat, sinking it. This suspended navigation on the canal for 48 hours until the lock gates could be replaced and the boat removed from the lock.<ref>{{cite web|url=http://www.nps.gov/history/history/online_books/choh/unrau_hrs.pdf|title=p. 812|website=nps.gov|access-date=21 September 2018}}</ref>