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74-485: The original artificial canal was 0.85 metres (33 in) deep and 7.5 metres (25 ft) wide; the man-made segment ran for 11.5 kilometres (7.1 mi), with a total length of 97 kilometres (60 mi) including the rivers it linked. The canal included seventeen wooden locks (of which the Palmschleuse at Lauenburg still exists) that managed the 13-metre (43 ft) elevation difference between its endpoints and

148-740: A flash lock . 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. They replaced earlier double slipways that had caused trouble and are mentioned by the Chinese polymath Shen Kuo (1031–1095) in his book Dream Pool Essays (published in 1088), and fully described in the Chinese historical text Song Shi (compiled in 1345): The distance between

222-404: A river more easily navigable, or to allow a canal to cross land that is not level. Later canals used more and larger locks to allow a more direct route to be taken. A pound lock is most commonly used on canals and rivers today. 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

296-528: A broad canal for more than one boat to be in a staircase at the same time, but managing this without waste of water requires expertise. On English canals, a staircase of more than two chambers is usually staffed: the lockkeepers at Bingley (looking after both the "5-rise" and the "3-rise") ensure that there are no untoward events and that boats are moved through as speedily and efficiently as possible. Such expertise permits miracles of boat balletics: boats travelling in opposite directions can pass each other halfway up

370-426: A flight of locks is simply a series of locks in close-enough proximity to be identified as a single group. For many reasons, a flight of locks is preferable to the same number of locks spread more widely: crews are put ashore and picked up once, rather than multiple times; transition involves a concentrated burst of effort, rather than a continually interrupted journey; a lock keeper may be stationed to help crews through

444-934: A key problem in such canals is ensuring a sufficient water supply. Important examples are the Chicago Portage , connecting the Great Lakes and Mississippi by the Chicago Sanitary and Ship Canal , and the Canal des Deux Mers in France, connecting the Atlantic and the Mediterranean. The name is enshrined at the Height of Land Portage on the route from the Great Lakes in the Atlantic drainage basin to

518-480: A lock is simple. For instance, if a boat travelling downstream finds the lock already full of water: If the lock were empty, the boat would have had to wait 5 to 10 minutes while the lock was filled. For a boat travelling upstream, the process is reversed; the boat enters the empty lock, and then the chamber is filled by opening a valve that allows water to enter the chamber from the upper level. The whole operation will usually take between 10 and 20 minutes, depending on

592-537: 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 9 in (23 cm) 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

666-480: A staircase lock can be used as an emergency dry dock). To avoid these mishaps, it is usual to have the whole staircase empty before starting to descend, or full before starting to ascend, apart from the initial chamber. One striking difference in using a staircase of either type (compared with a single lock, or a flight) is the best sequence for letting boats through. In a single lock (or a flight with room for boats to pass) boats should ideally alternate in direction. In

740-404: A staircase, however, it is quicker for a boat to follow a previous one going in the same direction. Partly for this reason staircase locks such as Grindley Brook, Foxton, Watford and Bratch are supervised by lockkeepers, at least during the main cruising season, they normally try to alternate as many boats up, followed by down as there are chambers in the flight. As with a flight, it is possible on

814-400: A tunnel, which when descending does not become visible until the chamber is nearly empty. A pound is the level stretch of water between two locks (also known as a reach ). 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

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888-439: Is a device used for raising and lowering boats , ships and other watercraft between stretches of water of different levels on river and canal waterways . 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. Locks are used to make

962-426: Is a normal top gate, and the intermediate gates are all as tall as the bottom gate). As there is no intermediate pound, a chamber can only be filled by emptying the one above, or emptied by filling the one below: thus the whole staircase has to be full of water (except for the bottom chamber) before a boat starts to ascend, or empty (except for the top chamber) before a boat starts to descend. In an "apparent" staircase

1036-443: Is only a staircase if successive lock chambers share a gate (i.e. do not have separate top and bottom gates with a pound between them). Most flights are not staircases, because each chamber is a separate lock (with its own upper and lower gates), there is a navigable pound (however short) between each pair of locks, and the locks are operated in the conventional way. However, some flights include (or consist entirely of) staircases. On

1110-806: Is the bifurcation of the Orinoco in the north of South America , whose main stream empties into the Caribbean , but which also drains into the South Atlantic via the Casiquiare canal and Amazon River . Since ridgelines are sometimes easy to see and agree about, drainage divides may form natural borders defining political boundaries, as with the Royal Proclamation of 1763 in British North America which coincided with

1184-575: Is the change in water-level in the lock. The two deepest locks on the English canal system are Bath deep lock on the Kennet and Avon Canal and Tuel Lane Lock on the Rochdale Canal , which both have a rise of nearly 20 feet (6.1 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,

1258-529: Is used in Canada and the United States to refer to a drainage divide. It is frequently used in border descriptions, which are set according to the "doctrine of natural boundaries ". In glaciated areas it often refers to a low point on a divide where it is possible to portage a canoe from one river system to another. Drainage divides can be divided into three types: A valley-floor divide occurs on

1332-680: The Urstromtäler , for example, between Havel and Finow in the Eberswalde Urstromtal . In marsh deltas such as the Okavango , the largest drainage area on earth, or in large lakes areas, such as the Finnish Lakeland , it is difficult to find a meaningful definition of a watershed. A bifurcation is where the watershed is effectively in a river bed, in a wetland, or underground. The largest watershed of this type

1406-746: The Black Sea and the Rienz into the Adriatic . Settlements are often built on valley-floor divides in the Alps. Examples are Eben im Pongau , Kirchberg in Tirol and Waidring (In all of these, the village name indicates the pass and the watershed is even explicitly displayed in the coat of arms). Extremely low divides with heights of less than two metres are found on the North German Plain within

1480-881: The Bollène lock on the River Rhône has a fall of at least 23 m (75 ft), the Leerstetten, Eckersmühlen and Hilpoltstein locks on the Rhine–Main–Danube Canal have a fall of 24.67 m (80.9 ft), each and the Oskemen Lock on the Irtysh River in Kazakhstan has a drop of 42 m (138 ft). The natural extension of the flash lock , or staunch, was to provide an upper gate (or pair of gates) to form an intermediate "pound" which

1554-476: The Grand Union . Operation of a staircase is more involved than a flight. Inexperienced boaters may find operating staircase locks difficult. The key worries (apart from simply being paralysed with indecision) are either sending down more water than the lower chambers can cope with (flooding the towpath, or sending a wave along the canal) or completely emptying an intermediate chamber (although this shows that

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1628-417: The Kennet and Avon Canal . Drainage divide A drainage divide , water divide , ridgeline , watershed , water parting or height of land is elevated terrain that separates neighboring drainage basins . On rugged land, the divide lies along topographical ridges , and may be in the form of a single range of hills or mountains , known as a dividing range . On flat terrain, especially where

1702-562: The Milan canal system sponsored by Francesco Sforza ) between 1452 and 1458. In Ancient Egypt, the river-locks was probably part of the Canal of the Pharaohs : Ptolemy II is credited by some 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. All pound locks have three elements: The principle of operating

1776-598: The Song dynasty (960–1279 CE). The Songshi or History of the Song Dynasty, volume 307, biography 66, records how Qiao Weiyue, a high-ranking tax administrator, was frustrated at the frequent losses incurred when his grain barges were wrecked on the West River near Huai'an in Jiangsu . The soldiers at one double slipway, he discovered, had plotted with bandits to wreck heavy imperial barges so that they could steal

1850-481: The Sound Dues and foreign shipping. In the fifteenth century traffic peaked, with more than 3,000 shipments of more than 30,000 tons of salt moving on the canal each year. This number declined by the seventeenth century to 400 to 600 shipments (5,000 to 7,000 tons). In 1789 there were still sixty-four shipments carrying approximately 680 tons of salt. Plans for a new Baltic–North Sea canal were proposed as early as

1924-585: The drainage divide between the North and Baltic Seas, with a summit height of 17 metres (56 ft) above sea level. In order to supply the top portion of the canal with water, flow was diverted from Hornbeker Mühlenbach . To the north the canal descended to the Ziegelsee by the town of Mölln and then connected to the Stecknitz by a series of eight locks. The southern end of the artificial canal descended to

1998-457: The towpath on the banks of the channel. By the 19th century newer vessel designs included rigging that eliminated the need for towing (with sufficient wind). In Lauenburg and Lübeck the barges were unloaded and their contents transferred to ships for export down the Elbe and Trave. Stecknitz bargees were only permitted to own one barge each, so they could not acquire great wealth in the trade; in

2072-541: The Baltic region. In the reverse direction the Stecknitz barges transported cereals , furs , herring , ash , timber and other goods from Lübeck, which were reloaded in Lauenburg and transported down the Elbe to Hamburg . Later coal , peat , brick , limestone and gravel were added to the cargo. The importance of the canal was greatest in years in which Øresund was closed to merchant ships because of disputes over

2146-689: The Carrapatelo and Valeira locks on the Douro river in Portugal, which are 279 feet (85 m) long and 39 feet (12 m) wide, have maximum lifts of 115 and 108 feet (35 and 33 m) respectively. The two Ardnacrusha locks near Limerick on the Shannon navigation in Ireland have a rise of 100 feet (30 m). The upper chamber rises 60 feet (18 m) and is connected to the lower chamber by

2220-466: The Chesapeake and Ohio Canal, the lockkeepers were required to remove the windlasses from all lock paddles at night, to prevent unauthorized use. A swell was caused by opening suddenly the paddle valves in the lock gates, or when emptying a lock. 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

2294-461: The Delvenau through a staircase of nine locks. The original salt barges measured roughly 12 metres (39 ft) by 2.5 metres (8.2 ft), with a 40-centimetre (16 in) draft when loaded to capacity with around 7.5 tons of salt, and required at least ten days to make the journey one way. When traveling uphill or through chamber locks the barges had to be hauled by laborers or animals walking

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2368-567: The Grand Union (Leicester) Canal, the Watford flight consists of a four-chamber staircase and three separate locks; and the Foxton flight consists entirely of two adjacent 5-chamber staircases. Where a very steep gradient has to be climbed, a lock staircase is used. There are two types of staircase, "real" and "apparent". A "real" staircase can be thought of as a "compressed" flight, where

2442-475: The advent of canals in Britain. The sides of the turf-lock are sloping so, when full, the lock is quite wide. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. On British canals and waterways most turf-sided locks have been subsequently rebuilt in brick or stone, and so only a few good examples survive, such as at Garston Lock , and Monkey Marsh Lock , on

2516-587: The boat entered the lock. Pulling on the rope slowed the boat, due to the friction of the rope against the post. A rope 2 + 1 ⁄ 2 inches (6.4 cm) in diameter and about 60 feet (18 meters) long was typically used on the Erie Canal to snub a boat in a lock. 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

2590-471: The bottom cill at all but the higher tides – the new bottom chamber rises just far enough to get the boat over the original lock cill. In China, the recently completed Three Gorges Dam includes a double five-step staircase for large ships, and a ship lift for vessels of less than 3000 metric tons. Examples of "apparent" staircases are Foxton Locks and Watford Locks on the Leicester Branch of

2664-799: The bottom of a valley and arises as a result of subsequent depositions, such as scree , in a valley through which a river originally flowed continuously. Examples include the Kartitsch Saddle in the Gail valley in East Tyrol , which forms the watershed between the Drau and the Gail, and the divides in the Toblacher Feld between Innichen and Toblach in Italy , where the Drau empties into

2738-641: The canal would cause frequent interruptions of the heavy road traffic. It can be emptied by pumping – but as this uses a lot of electricity the method used when water supplies are adequate is to drain the lock to a nearby burn . In 2016 the Kieldrecht Lock in the Port of Antwerp in Belgium took over the title of the world's largest lock from the Berendrecht Lock in the same port and still has

2812-544: The chambers so that some water from the emptying chamber helps to fill the other. This facility has long been withdrawn on the English canals, although the disused paddle gear can sometimes be seen, as at Hillmorton on the Oxford Canal . Elsewhere they are still in use; a pair of twinned locks was opened in 2014 on the Dortmund–Ems Canal near Münster , Germany. The once-famous staircase at Lockport, New York ,

2886-631: The chambers still have common gates, but the water does not pass directly from one chamber to the next, going instead via side ponds. This means it is not necessary to ensure that the flight is full or empty before starting. Examples of famous "real" staircases in England are Bingley and Grindley Brook . Two-rise staircases are more common: Snakeholme Lock and Struncheon Hill Lock on the Driffield Navigation were converted to staircase locks after low water levels hindered navigation over

2960-404: The chance of a boat finding a lock set in its favour. There can also be water savings: the locks may be of different sizes, so that a small boat does not need to empty a large lock; or each lock may be able to act as a side pond (water-saving basin) for the other. In this latter case, the word used is usually "twinned": here indicating the possibility of saving water by synchronising the operation of

3034-496: The cill bumper. Some canal operation authorities, primarily in the United States and Canada, call the ledge a miter sill (mitre sill in Canada). 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 ,

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3108-523: The concept has been suggested in a number of cases, the only example in the world of a drop lock that has actually been constructed is at Dalmuir on the Forth and Clyde Canal in Scotland. This lock, of the single-chamber type, was incorporated during the restoration of the canal, to allow the replacement of a swing bridge (on a busy A road) by a fixed bridge, and so answer criticisms that the restoration of

3182-651: The construction of an artificial canal between the Elbe and the Baltic Sea. Construction on the canal began in 1391; thirty barges carrying the first load of salt from Lüneburg reached Lübeck on 22 July 1398. The Stecknitz Canal soon replaced the existing overland cart road as the main transport mode for Lüneburg salt on the Old Salt Route . In Lübeck the salt was stored in vast salt warehouses and then transferred to ocean-going vessels for export throughout

3256-425: The flight quickly; and where water is in short supply, a single pump can recycle water to the top of the whole flight. The need for a flight may be determined purely by the lie of the land, but it is possible to group locks purposely into flights by using cuttings or embankments to "postpone" the height change. Examples: Caen Hill locks, Devizes . "Flight" is not synonymous with "Staircase" (see below). A set of locks

3330-518: The form of the now-disused Écluse des Lorraines , connecting the Canal latéral à la Loire with the River Allier . A drop lock can consist of two conventional lock chambers leading to a sump pound, or a single long chamber incorporating the sump – although the term properly applies only to the second case. As the pounds at either end of the structure are at the same height, the lock can only be emptied either by allowing water to run to waste from

3404-527: The full journey from Lauenburg to Lübeck stretched to a distance of 97 kilometres (60 mi), even though the straight-line separation between the two cities is only 55 kilometres (34 mi). The journey along the canal often lasted two weeks or longer due to the number and primitive design of the locks and the difficulty of towing. The canal's course originally included thirteen locks , which later renovations increased to seventeen. Initially most were one-gate flash locks built into weirs (usually set below

3478-405: The ground is marshy , the divide may be difficult to discern. A triple divide is a point, often a summit , where three drainage basins meet. A valley floor divide is a low drainage divide that runs across a valley , sometimes created by deposition or stream capture . Major divides separating rivers that drain to different seas or oceans are continental divides . The term height of land

3552-583: The highest central part, the Delvenaugraben . In the Middle Ages the trade between the North Sea and Baltic Sea grew dramatically, but the sea journey through Øresund , increasingly important to commercial shipping since the thirteenth century, was time-consuming and dangerous. Therefore, the emerging Hanseatic city of Lübeck and Eric IV of Saxe-Lauenburg agreed in 1390 to cooperate in

3626-414: The intermediate pounds have disappeared, and the upper gate of one lock is also the lower gate of the one above it. However, it is incorrect to use the terms staircase and flight interchangeably: because of the absence of intermediate pounds, operating a staircase is very different from operating a flight. It can be more useful to think of a staircase as a single lock with intermediate levels (the top gate

3700-403: The lock gates could be replaced and the boat removed from the lock. To economise, especially where good stone would be prohibitively expensive or difficult to obtain, composite locks were made, i.e. they were constructed using rubble or inferior stone, dressing the inside walls of the lock with wood, so as not to abrade the boats. This was done, for instance, on the Chesapeake and Ohio Canal with

3774-403: 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. 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

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3848-757: The locks near the Paw Paw Tunnel . and also the Chenango Canal On large modern canals, especially very large ones such as ship canals , the gates and paddles are too large to be hand operated, and are operated by hydraulic or electrical equipment. On the Caledonian Canal the lock gates were operated by man-powered capstans , one connected by chains to open the gate and another to draw it closed. By 1968 these had been replaced by hydraulic power acting through steel rams. The construction of locks (or weirs and dams) on rivers obstructs

3922-446: The long run this ensured their dependence upon the Lübeck salt merchants, who were not bound by any such limitations and amassed great fortunes. The guild of the Stecknitzfahrer (Stecknitz bargees) still exists today in Lübeck and meets annually at the Kringelhöge to celebrate the guild's history. 53°39′N 10°39′E  /  53.650°N 10.650°E  / 53.650; 10.650 Lock (water navigation) A lock

3996-418: The mouth of a tributary creek), where water was dammed until a barge was ready to pass downriver. In Lauenburg the initial course included one chamber lock (the Palmschleuse ) because of a watermill whose operation would have been made impossible by a flash lock. Over the course of the canal's lifetime further flash locks were progressively converted to chamber locks until the 17th century. The canal overcame

4070-419: The new canal was low. This resulted in a sequential pair of locks, with gates pointing in opposite directions: one example was at Hall Green near Kidsgrove , where the southern terminus of the Macclesfield Canal joined the Hall Green Branch of the earlier Trent and Mersey Canal . The four gate stop lock near Kings Norton Junction, between the Stratford-upon-Avon Canal and the Worcester and Birmingham Canal

4144-406: The north-flowing Stecknitz and south-flowing Delvenau . The man-made trench itself was about 85 centimetres (33 in) deep and 7.5 metres (25 ft) wide, though it was enlarged between 1821 and 1823 to a depth of 144 centimetres (57 in) and a width of 12 metres (39 ft). Outside the artificial segment the canal followed the tortuous natural watercourses of the two rivers; as a result,

4218-528: The passage of fish. Some fish such as lampreys, trout and salmon go upstream to spawn. Measures such as a fish ladder are often taken to counteract this. Navigation locks have also potential to be operated as fishways to provide increased access for a range of biota. Locks can be built side by side on the same waterway. This is variously called doubling , pairing , or twinning . The Panama Canal has three sets of double locks. Doubling gives advantages in speed, avoiding hold-ups at busy times and increasing

4292-510: The ridgeline of the Appalachian Mountains forming the Eastern Continental Divide that separated settled colonial lands in the east from Indian Territory to the west. Another instance of a border matching a watershed in modern times involves the western border between Labrador and Quebec , as arbitrated by the privy council in 1927. Drainage divides hinder waterway navigation . In pre-industrial times, water divides were crossed at portages . Later, canals connected adjoining drainage basins;

4366-547: The seventeenth century, but none was implemented until the end of the nineteenth century, when the new Elbe–Lübeck Canal was built using parts of the old route of the Stecknitz Canal. For five hundred years the canal was used to transport the "white gold" and other goods; today the Palmschleuse lock in Lauenburg is one of the last remaining parts of the former canal, preserved as an historical monument. The Stecknitz Canal consisted of an 11.5-kilometre (7.1 mi) artificial waterway (the Delvenaugraben ) linking two minor rivers,

4440-469: The size of the lock and whether the water in the lock was originally set at the boat's level. Boaters approaching a lock are usually pleased to meet another boat coming towards them, because this boat will have just exited the lock on their level and therefore set the lock in their favour – saving about 5 to 10 minutes. However, this is not true for staircase locks, where it is quicker for boats to go through in convoy, and it also uses less water. The rise

4514-407: The spilled grain. In 984 Qiao installed a pair of sluice-gates two hundred and fifty feet apart, the entire structure roofed over like a building. By siting two staunch gates so close to one another, Qiao had created a short stretch of canal, effectively a pound-lock, filled from the canal above by raising individual wooden baulks in the top gate and emptied into the canal below by lowering baulks in

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4588-411: The staircase by moving sideways around each other; or at peak times, one can have all the chambers full simultaneously with boats travelling in the same direction. When variable conditions meant that a higher water level in the new canal could not be guaranteed, then the older company would also build a stop lock (under its own control, with gates pointing towards its own canal) which could be closed when

4662-413: The sump to a lower stream or drain, or (less wastefully) by pumping water back up to the canal. Particularly in the two-chamber type, there would be a need for a bypass culvert, to allow water to move along the interrupted pound and so supply locks further down the canal. In the case of the single-chamber type, this can be achieved by keeping the lock full and leaving the gates open while not in use. While

4736-438: The title for largest volume. In 2022 the IJmuiden sea lock serving the Port of Amsterdam became the world's largest lock by surface area. The lock is 500 m (1,600 ft) long, 70 m (230 ft) wide and has sliding lock gates creating a usable depth of 18 m (59 ft). The size of locks cannot be compared without considering the difference in water level that they are designed to operate under. For example,

4810-400: The top gate and raising ones in the lower. A turf-sided lock is an early form of canal lock design that uses earth banks to form the lock chamber, subsequently attracting grasses and other vegetation, instead of the now more familiar and widespread brick, stone, or concrete lock wall constructions. This early lock design was most often used on river navigations in the early 18th century before

4884-403: 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. The water level could differ by 4 or 5 feet (1.2 or 1.5 m) at each lock and in the Grand Canal the level

4958-416: 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. 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

5032-453: The whole pound below. 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. The Erie Canal management did not like swelling for two reasons. First, it used too much water lowering

5106-399: Was all that need be emptied when a boat passed through. This type of lock, called a pound lock was known in Imperial China and ancient Europe and was used by Greek engineers in the Canal of the Pharaohs under Ptolemy II (284 to 246 BC), when engineers solved the problem of overcoming the difference in height through canal locks . Pound locks were first used in medieval China during

5180-422: 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

5254-416: Was also a doubled set of locks. Five twinned locks allowed east- and west-bound boats to climb or descend the 60 feet (18 m) Niagara Escarpment , a considerable engineering feat in the nineteenth century. While Lockport today has two large steel locks, half of the old twin stair acts as an emergency spillway and can still be seen, with the original lock gates having been restored in early 2016. Loosely,

5328-412: Was invented by Leonardo da Vinci sometime around the late 15th century. 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. On

5402-456: Was raised in this way by 138 feet (42 m). In medieval Europe a sort of pound lock was built in 1373 at Vreeswijk , Netherlands. This pound lock serviced many ships at once in a large basin . Yet the first true pound lock was built in 1396 at Damme near Bruges , Belgium. The Italian Bertola da Novate (c. 1410–1475) constructed 18 pound locks on the Naviglio di Bereguardo (part of

5476-553: Was replaced in 1914 by a pair of guillotine lock gates which stopped the water flow regardless of which canal was higher. These gates have been permanently open since nationalisation. The best known example of a round lock is the Agde Round Lock on the Canal du Midi in France. This serves as a lock on the main line of the canal and allows access to the Hérault River . A second French round lock can be found in

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