Editing Lock (water navigation) (section)

==Alternatives==
===Inclined plane===
There are no working waterway inclined planes in the UK at the moment, but the remains of a famous one can be seen at [[Foxton inclined plane|Foxton]] in Leicestershire on the Leicester arm of the [[Grand Union Canal]]. The plane enabled wide-beam boats to bypass the flight of ten narrow locks, but failure to make improvements at the other end of the arm and high running costs led to its early demise.<ref>[[Nicholson Guides|Nicholson Waterways Guide]], Volume 3, Harper Collins Publishers, {{ISBN|0-00-713666-8}}</ref> There are plans to restore it, and some funding has been obtained.<ref>{{cite web|url=http://www.fipt.org.uk/lift.html |title=Foxton Inclined Plane Trust: Restoration |publisher=Fipt.org.uk |access-date=2011-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20110927044301/http://www.fipt.org.uk/lift.html |archive-date=2011-09-27 }}</ref>

===Caisson lock===
[[File:Caisson lockenglish.svg|thumb|Operation of caisson lock]]
{{Main|Caisson lock}}
Around 1800 the use of caisson locks was proposed by [[Robert Weldon]]<ref>[https://canalrivertrustwaterfront.org.uk/heritage/speedy-invention/ Robert Weldon]</ref> for the [[Somerset Coal Canal]] in England. In this underwater lift, the chamber was {{cvt|80|ft|m|1}} long and {{convert|60|ft|m|1|abbr=on}} deep and contained a completely enclosed wooden box big enough to take a barge. This box moved up and down in the {{convert|60|ft|m|1|abbr=on}} deep pool of water. Apart from inevitable leakage, the water never left the chamber, and using the lock wasted no water. Instead, the boat entered the box and was sealed in by the door closing behind it, and the box itself was moved up or down through the water. When the box was at the bottom of the chamber, it was under almost {{convert|60|ft|m|1}} of water – at a pressure of {{cvt|3|atm|kPa psi|sigfig=3|spell=in|lk=on}}, in total. One of these "locks" was built and demonstrated to the Prince Regent (later [[George IV of the United Kingdom|George IV]]), but it had various engineering problems and the design was not put into use on the Coal Canal.<ref>{{cite web|title=The Somerset Coal Canal|work=Bath Royal Literary and Scientific Institution |url=http://www.brlsi.org/proceed03/transport200201.htm |access-date=6 October 2006 |url-status=dead |archive-url=https://web.archive.org/web/20061114001751/http://www.brlsi.org/proceed03/transport200201.htm |archive-date=14 November 2006}}</ref><ref>{{cite web|title=History of the Caisson Lock On the Somersetshire Coal Canal |work=The Somersetshire Coal Canal (Society) |url=http://rtjhomepages.users.btopenworld.com/caishist.html |access-date=6 October 2006 |url-status=dead |archive-url=https://web.archive.org/web/20061011094639/http://rtjhomepages.users.btopenworld.com/caishist.html |archive-date=11 October 2006 }}</ref>

=== Hydro-pneumatic canal lift ===
Possibly inspired by Weldon's caisson lock, [[Sir William Congreve, 2nd Baronet|William Congreve]] in 1813 patented a "hydro-pneumatic double balance lock" in which two adjacent locks containing [[Caisson (engineering)|pneumatic caissons]] could be raised and lowered in counterbalance by the movement of compressed air from one caisson to the other. In about 1817 the [[Regents Canal|Regents Canal Company]] built one of these locks at the site of the present-day [[Camden Lock]], north London. Here the motivation was, again, water supply problems. The company insisted on various modifications to Congreve's design; the resulting installation proved to be unsatisfactory, and was soon replaced by conventional locks.<ref>{{cite web | title=Congreve's Hydro-Pneumatic Canal Lift – A Humbug! | work=London Canals | url=http://www.londoncanals.co.uk/history/cgrv.html | access-date=25 September 2013 | url-status=dead | archive-url=https://web.archive.org/web/20130927132632/http://www.londoncanals.co.uk/history/cgrv.html | archive-date=27 September 2013 }}</ref><ref>Faulkner, Alan (2005): ''The Regent's Canal: London's Hidden Waterway''. Waterways World Ltd. {{ISBN|1-870002-59-8}}.</ref>

===Shaft lock===
[[File:Minden Weser-Mittelland Kanal Lock 01.jpg|thumb|left|Entrance to Minden shaft lock]]
Looking superficially similar to the caisson lock is the shaft lock. Shaft locks consist of a deep shaft with conventional upper gates. The lower gates are reached through a short tunnel. The gates only close off this approach tunnel so do not have to reach the full height of the lock. Notable examples have been built at Saint Denis (Paris, France), Horin (near Melnik, Czech Republic) and Anderten (Hannover Germany).<ref>{{cite web|title=The International Canal Monuments List|editor-last=Hughes|editor-first=Stephen|publisher=ICOMOS (the International Council on Monuments and Sites)|url=http://www.icomos.org/studies/canals.pdf|access-date=2015-09-06|archive-url=https://web.archive.org/web/20130810162849/http://www.icomos.org/studies/canals.pdf|archive-date=2013-08-10|url-status=dead}}</ref> 

The shaft lock at Minden {{Coord|52|18|23|N|8|55|11|E}} has a fall of {{convert|12.7|m}} and has eight tanks linked in pairs to the lock chamber.<ref>{{cite book|last=Hadfield|first=Charles|title=World Canals: Inland Navigation Past and Present|publisher=David & Charles| isbn=0-7153-8555-0|date=1986|page=162}}</ref>  As the lock is emptied water is run into each chamber in turn, for filling the water is released from the chambers thus saving the waste of a complete lockfull of water. An earlier attempt at a shaft lock had been made at Trollhättan in Sweden on the line of the present Göta canal. The fall would have been {{convert|16|m}}, astonishing in 1749. However the approach tunnel proved to be unusable in times of flood and the shaft lock was replaced by a 2-rise staircase in 1768.<ref>Hadfield (1986) p. 55.</ref>

===Diagonal lock===
[[File:TGDModelShipLocks.jpg|thumb|[[Three Gorges Dam]] model view. A pair of five locking steps is at center with a ship lift to the left.]]

This is similar to a shaft lock, but having the shaft built on an incline. Boats are moored to floating bollards which guide them along the shaft as it fills or empties. The "Diagonal Lock Advisory Group" has identified several sites in Britain where the new design could be installed, either on new waterways or canals under restoration.<ref>{{cite web| last = Fogarty| first = Terry| title = Diagonal Lock – Overview| year = 2008| url = http://www.diagonallock.org/overview.htm| access-date = 6 November 2016| archive-url = https://web.archive.org/web/20170215072534/http://www.diagonallock.org/overview.htm| archive-date = 15 February 2017| url-status = dead}}</ref> Projects under consideration include the restoration of the [[Lancaster Canal]] to [[Kendal]] and the proposed new branch of the [[Grand Union Canal#New branch|Grand Union Canal]] between [[Bedford]] and [[Milton Keynes]].