Caisson lock

Operation of caisson lock
Contemporary engraving of the lock at Combe Hay

Type of canal lock in which a narrowboat is floated into a sealed watertight box and raised or lowered between two different canal water levels.

- Caisson lock

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Caisson (engineering)

Watertight retaining structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships.

Schematic cross section of a pressurized caisson
Pneumatic caisson, supplied with Compressed Air

Boat lift caissons: The word caisson is also used as a synonym for the moving trough part of caisson locks, canal lifts and inclines in which boats and ships rest while being lifted from one canal elevation to another; the water is retained on the inside of the caisson, or excluded from the caisson, according to the respective operating principle.

Lock (water navigation)

Device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways.

Canal lock and lock-keeper's cottage on the Aylesbury Arm of the Grand Union Canal at Marsworth in Hertfordshire, England
Lock on the River Neckar at Heidelberg in Germany
Three Gorges Dam lock near Yichang on Yangtze river, China
A gate in the Hatton flight in England
Iroquois Lock on the Saint Lawrence Seaway
A pound lock on the Keitele–Päijänne Canal at Äänekoski in Central Finland
A plan and side view of a generic, empty canal lock. A lock chamber separated from the rest of the canal by an upper pair and a lower pair of mitre gates. The gates in each pair close against each other at an 18° angle to approximate an arch against the water pressure on the "upstream" side of the gates when the water level on the "downstream" side is lower.
Operation of a canal lock 
1–3. Boat enters 'empty' lock 
4. Bottom gates are closed, bottom paddles closed, top paddles opened, lock starts to fill 
5. Lock is filling with water, lifting boat to the higher level
Collection of lock windlasses. Note: rakes are for clearing trash out of the lock.
Snubbing a boat to keep it from hitting the downstream gates. Note the rope wrapped around the snubbing post.
Doubled locks. Left lock has boat in it, right lock (center of drawing) is empty. This is on the Erie Canal at Lockport.
Agde Round Lock
Dalmuir drop lock
Berendrecht Lock (right) and Zandvliet Lock (left), located at the entrance to the Port of Antwerp (top) from the Scheldt (foreground)
Barges at a lock on the Mississippi River
Model of early river pound lock, constructed in Lankheet water park, Netherlands
The turf-sided Monkey Marsh Lock on the Kennet & Avon Canal at Thatcham
Operation of caisson lock
Entrance to Minden shaft lock
Three Gorges Dam model view. A pair of five locking steps is at center with a ship lift to the left
The cill exposed in the deep Pont de Flandre lock on the Canal Saint-Denis, Paris
Top gate of a lock, showing the balance beams and paddle winding gear
200-year-old paddle gear on the Wiener Neustädter Kanal, Austria
Water conservation gear on the Birmingham Canal Navigations
Lock gate controls on a canal

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.

Camden Lock

Small part of Camden Town, London Borough of Camden, England, which was formerly a wharf with stables on the Regent's Canal.

The twin locks
A warm summer day at Camden Lock
Camden Lock panorama at sunset.
The Interchange building, where goods were transferred to canal boats, is now the offices of Associated Press Television News.
The North London line railway bridge over Chalk Farm Road from Camden Lock Place, a pedestrian-only road with open-air and permanent stalls, and entrances to some of the Camden markets

Colonel William Congreve, a military engineer who was later knighted, proposed the use of hydropneumatic boat lifts instead of locks.

Boat lift

Machine for transporting boats between water at two different elevations, and is an alternative to the canal lock.

Strépy-Thieu boat lift (Belgium, Wallonia)
The Falkirk Wheel (Scotland)
Peterborough Lift Lock (Canada)

It lifted boats 7 m using a moveable hoist rather than caissons.

Combe Hay

Village and civil parish in the English county of Somerset.

The Fuller's Earth Works at Combe Hay in 2015
Weir on Cam Brook at Combe Hay
Derelict lock on the Somerset Coal Canal next to Caisson House

It is the site of one of the only caisson locks ever built which was near the current Caisson House.

Tardebigge Locks

Longest flight of locks in the UK, comprising 30 narrow locks on a 2+1/4 mi stretch of the Worcester and Birmingham Canal at Tardebigge, Worcestershire.

Some of the Tardebigge locks from the embankment of Tardebigge Reservoir
Tardebigge Top Lock, with a rise of 11 ft, and keeper's cottage
Inland Waterways Association plaques at Tardebigge top lock
Inland Waterways Association plaque 1981 with incorrect date of founding
Inland Waterways Association plaque 2005 with correct date

The 64-ton wooden caisson (lifting chamber) was sealed at each end by guillotine gates, as was the lock chamber.

Transport in Somerset

[[File:Somerset numbered districts 2019.svg|thumb|200px|Districts of Somerset County council area:

Somerset in England
A replica of the Sweet Track
Roman roads showing the Fosse Way
The George Inn, Norton St Philip, once a coaching inn
Dunball Wharf. To the right is Dunball Clyce where the King's Sedgemoor Drain flows into the River Parrett.
Firepool Lock where the Bridgwater and Taunton Canal joins the River Tone
Pleasure steamers at Birnbeck Pier, Weston-super-Mare
Taunton railway station in 1892
Railways in Somerset c1930
after closure
A "toast rack" tram in
Weston-super-Mare
A preserved Southern National bus (built in 1951) in Taunton
Crosville (left) and Webberbus services in Weston-super-Mare, 2015
The M5 motorway crossing the Somerset Levels near Brent Knoll
One of The Buses of Somerset near Williton
Great Western Railway service to London at
A container ship at Royal Portbury Dock
Bristol Airport

This was initially done by the use of Caisson locks.

Erasmus Darwin

English physician.

Erasmus Darwin c. 1792–1793, oil painting by Joseph Wright of Derby, Derby Museum and Art Gallery
Stone-cast bust of Erasmus Darwin, by W. J. Coffee, c. 1795
Darwin's House in Lichfield, now a museum dedicated to his life and work.
Joseph Wright of Derby, Erasmus Darwin (1770; Birmingham Museum and Art Gallery).
Erasmus Darwin's coat of arms. Escutcheon: Argent, on a bend Gules cottised Vert, three escallop shells, Or. Crest: A demi-griffin segreant, Vert, holding in his claws an escallop, Or. Motto: E conchis omnia (All things out of conches/molluscs).
Erasmus Darwin in stipple engraving by Holl, 1803, after J. Rawlinson
580px

He also inspired Robert Weldon's Somerset Coal Canal caisson lock.

Combe Hay Locks

Derelict flight of locks on the Somerset Coal Canal near Combe Hay, Somerset, England.

The chambers of locks 14, 13 and 12
John Billingsley's engraving of the caisson lock at Combe Hay

Twenty two locks raised the canal 134 ft over approximately 1.6 mi. The lock flight was predated in the immediate area by two other methods of canal lifts—first by a series of caisson locks, then by an inclined plane.

Somerset Coal Canal

Narrow canal in England, built around 1800.

House at Tucking Mill, next to the canal, reputedly lived in by William Smith
Derelict lock next to Caisson House, Combe Hay
Somerset Coal Canal at Dundas Aqueduct
Portrait of John Rennie, 1810, by Sir Henry Raeburn
William Smith
Operation of caisson lock
Outlet view of spillway drain 25 ft long and 10 ft wide
Internal view of spillway drain about 66 ft in length
The spoil tip in Paulton, referred to locally as "The Batch"
Aqueduct on the Somerset Coal Canal at Dunkerton
The canal in 2006: moorings on the only navigable section of the canal, near its junction with the Kennet and Avon Canal. This stretch at Brassknocker, 200 m long, is used for moorings, a café, and boat and cycle hire.
Excavated canal dry dock and restored entrance arch at Paulton Basin, on the Somerset Coal Canal.
The restored canal bed at Upper Midford to the west of the recently uncovered Georgian spillway drain

A feature of the canal was the variety of methods used at Combe Hay to overcome height differences between the upper and lower reaches: initially by the use of caisson locks; when this method failed an inclined plane trackway; and finally a flight of 22 conventional locks.