An Encyclopedia of the History of Technology part 51 ppsx

PART THREE: TRANSPORT 482 an Act was obtained in 1885 but the Manchester Ship Canal Company had to repurchase the old Bridgewater Canal from the railways and they had difficulty in raising the capital. The target was reached with a month to spare. Work commenced in 1887 and at times 17,000 men, with a great deal of novel mechanical equipment, were employed on cutting the canal. Construction included the entrance locks at Eastham and four other sets of locks. Brindley’s original aqueduct was replaced by the Barton Swing Aqueduct. At the Manchester end a dock system was established which became very busy with cotton and grain traffic. Through sailings started on 1 January 1894 and the canal was formally opened on 21 May 1894. Additional docks nearer the Liverpool end were opened in 1922 and 1933 and a new Queen Elizabeth II dock for oil tankers at Eastham, just below the entrance to the Ship Canal, in 1954. With the decline of the cotton industry and the changing pattern of sea transport the Manchester Ship Canal also became moribund. Sir Edward Leader Williams, who before becoming engineer to the Manchester Ship Canal had been engineer to the Weaver Navigation, had conceived the idea of constructing a lift between the Weaver and the Trent and Mersey Canal at Anderton to overcome a difference in levels of 15m (50ft) and the design by Edwin Clark was the progenitor of several lifts on the Continent. Completed in 1875, it was built as a hydraulically counterbalancing lift with two tanks supported on pistons. The cylinders in which the pistons worked were interconnected and the flow of hydraulic fluid could be started and stopped by opening and closing a valve in the connecting pipe, so that the descent of one tank controlled the ascent of the other. In 1882 one cylinder burst and both cylinders were renewed but by 1905 corrosion was affecting both cylinders again and it was decided to convert the lift to two independent tanks, each counterbalanced by a series of weights suspended on cables carried over 2m diameter pulleys mounted on the summit of the structure. During the first half of the twentieth century the carriage of bulk materials, coal, timber and grain, steadily passed to rail and then road transport. For example, the Lee traffic, which had consisted mainly of these three types of cargo, fell from over 610,000 tonnes in 1911 to an occasional barge in the 1960s. In 1948 most of the canals in the United Kingdom were nationalized, coming ultimately under the control of the British Waterways Board. Commercial traffic soon fell to negligible proportions on the narrow canals, and was gradually replaced by a thriving leisure industry aided by an energetic campaign for canal preservation, (see p. 516). FRANCE In mediaeval France water carriage was mainly served by the great rivers such as the Loire, Seine, Rhône, Somme, Saône and Dordogne, and although the INLAND WATERWAYS 483 Romans had suggested a link between the Moselle and the Saône the first major French canal was not started until the seventeenth century. Even river navigation was to a much lower standard than would be acceptable later. Traffic was mainly downstream, either using rafts of timber as on the Sarre, where they could be floated down to water-powered sawmills on the banks, or on purpose-constructed boats, as on the Dordogne and elsewhere, which at the end of a single voyage could be disassembled and their timber sold. The demand for timber from Holland for naval construction led to a considerable traffic in rafts down the Sarre, Moselle and Rhine. Even the busiest river in France, the Loire, was only navigable from All Saints to Pentecost (November to April) each year. At the beginning of the sixteenth century the return of Francis I to France accompanied by Leonardo da Vinci turned ideas to linking rivers to provide a through route between the Mediterranean and the Atlantic, avoiding the long haul round the Iberian Peninsula. Two proposals were actively considered, neither of which came to fruition at the time but which were later to be built as canals; one linking the Saône and the Loire and the other Garonne and the Mediterranean. By the end of the sixteenth century the growing demands of Paris for food, plentifully available in the Loire valley, stimulated Henry IV and his adviser the Due de Sully into considering a link between the Seine and the Loire. Surveys were made and a scheme prepared by Hugues Cosnier was approved on 11 March 1604 whereby a canal would be built from Briare on the Loire to Montargis on the Loing. The Loing was navigable and joined the Seine to reach Paris. Work started in 1605 but was abandoned following the assassination of the king in 1610. By then 42km (26 miles) had been constructed together with 35 locks, which included a seven-rise staircase at Rogny. Recommendation for its completion was made in 1628 but it was not until 1638 that authorization to resume was granted by Louis XIII to Guillaume Boutheroue and Jacques Guyon, Sieur du Chesnoy. The canal was completed in 1642 and became the second summit level canal, and the first modern one, in Europe. The seven-rise staircase of locks at Rogny, a remarkable civil engineering development at the time, was superseded in 1887 by six individual locks but the remains of the staircase are still to be seen, a tribute to the builders. The Canal de Briare is still in use with a recent modern feature—the longest canal aqueduct in the world across the Loire at Briare. Completed in 1896 and designed by Gustave Eiffel, it is 662m (2172ft) long consisting of an iron trough mounted on 15 piers. With facilities for draining it into the Loire, it links the Canal de Briare with the early nineteenth-century Canal Lateral à la Loire and obviated a difficult level crossing over the Loire. In the south of the country the valley between the Massif Central to the north and the foothills of the Pyrenees to the south suggested the site for a waterway link between the Mediterranean and the Atlantic and various PART THREE: TRANSPORT 484 surveys were made. Nicholas Bachelier, instructed by Francis I in the sixteenth century, proposed a canal from the Garonne at Toulouse to the Aude and into the Mediterranean and this was the first survey of many. One of the problems was the supply of water to the summit level. This was solved by the 50-year- old Pierre Paul Riquet, a native of Beziers, who, with no previous experience of canal engineering, realized how the waters of the Montagne Noire could be tapped and used as feeders for the summit level. Ultimately, after further delay but with the recommendations of the Archbishop of Toulouse and of Colbert, Minister of Finance, Riquet was granted a patent on 18 November 1666 to construct the canal in eight years by January 1675: he was then 62. Though work was pushed forward with great pertinacity—there were at the peak period 12,000 working on construction—many new difficulties, both physical and financial, conspired to delay completion. Riquet died on 1 October 1680, prevented by a few weeks from seeing his final triumph, for the official opening of the Canal du Midi took place in the presence of many dignitaries on 15 May 1681. Riquet’s solution to the summit-level water supply was to divert water from the small rivers flowing down from the Montagne Noire into a large reservoir, the Bassin de St Ferreol, and then down the mountain in a feeder into a holding basin at Naurouze. The dam for the St Ferreol reservoir was the first for water for a navigable canal and was the biggest civil engineering undertaking on the project. This was supplemented in 1791 by a second, smaller, reservoir, the Bassin de Lampy. From Naurouze water was available to supply the locks both to the east and the west. That this solution was effective has been proved by its continued use for 300 years. A second important contribution made by Riquet was the world’s first canal tunnel, the Malpas tunnel 165m (541ft) in length. One end is still unlined and the winds of three centuries have eroded the soft friable rock so that it looks like the entrance to a cavern. Riquet’s third triumph was the construction of an eight-lock staircase at Fonserannes on the opposite bank of the Orb from Beziers. This flight was bypassed in 1985 by a water slope similar to the one constructed on the Canal Lateral à la Garonne at Montech. Originally the canal crossed the Orb at Beziers on the level, but in 1856 a new line leading from the seventh lock on the Fonserannes staircase was constructed leading to the present aqueduct across the river. This was built with the architectural grandeur commensurate with Riquet’s original conception. A further problem on the canal which received a unique solution was the level crossing of the river Libron, west of Agde. Here the bed of the canal is actually below sea level, and as the Libron is liable to bring down large quantities of silt in flash floods which could not be cleared by scouring. Riquet devised a flat-topped barge which could be sunk in the bed of the canal so that the flood water passed over its deck without diminishing the flow velocity and allowing the silt to settle out of suspension into the lower canal bed. This has INLAND WATERWAYS 485 been superseded by a structure diverting the Libron’s flow alternately into one of two channels separated on the canal by a chamber the length of a barge like a lock chamber with gates at each end. Each of the channels has a deck which can be lowered over the canal so that the flood water passes over this. As the barge passes through the chamber the flood water can be directed first through one channel and then the second so that its flow is not impeded. This ensures that the canal can still be used even though the Libron is in flood. The 240km (149 mile) long Canal du Midi provided half the distance of the link between the Mediterranean and the Atlantic, but it did not overcome the difficulties of navigation on the Garonne between Toulouse and Bordeaux. Bypassing at least part of this section was first proposed by Riquet, but authorization had to wait until 1838. It was then agreed that a 194km (120.5 mile) lateral canal should be built, leaving only the 54km (33.5 miles) between Castets- en-Dorthe and Bordeaux with the navigation in the tidal Garonne. The Canal Lateral à la Garonne was opened from Toulouse to Agen in 1850 and completed in 1856. It includes the 539m (1768ft) long masonry aqueduct over the Garonne near Agen. Between Toulouse and Noissec near the short branch canal to Montauban are the five locks at Montech which were bypassed in 1974 by the experimental water slope. This is one of the most significant developments in inland waterway engineering since the invention of the pound lock. The water slope, designed by Professor Jean Aubert, Inspecteur-Général des Ponts et Chaussées, consists of an inclined rectilinear concrete flume linking the upper and lower pounds of the canal. A wedge of water in which the barge floats is pushed up the slope by a moveable dam, rather like a giant bulldozer blade, called a shield. At the top of the slope the wedge of water makes a level with the surface in the upper pound and the gate which holds back the upper pound falls under the pressure of the wedge. To propel the shield at Montech two 1000hp diesel-electric locomotives are used. The controls are linked so that one unit is a slave to the other manned unit. The units are mounted on rubber tyres to give better adhesion up and down the slope, but there is also a raised continuous plinth against which horizontal guide wheels mounted beneath the unit, run to keep the unit on the set track. The shield has neoprene rollers mounted on the two sides and the bottom to squeegee against the contour of the flume, ensuring minimal loss of water from the wedge. The slope of the flume is three per cent and its effective length of 443m (1453ft) gives a change in level between the upper and lower pounds of 13.3m (43.6ft) (equivalent to five locks). In front of the shield there is a cradle with two arms which adapt to the shape of the bow or stern of the barge. The speed of travel is 4.5kph (2.8mph). The experiment was a success and a similar slope was constructed and is in operation at the Fonserannes staircase at Beziers on the Canal du Midi. The German authorities also carried out a feasibility study with a view to its use at Scharnebeck on the Elbe Seiten Canal but in the end decided on a lift instead. PART THREE: TRANSPORT 486 In the north progress on the Canal du Midi was watched with interest and immediately after its completion the Due d’Orléans, Louis XIV’s brother, obtained a concession to build the Canal d’Orléans to link Orleans on the Loire with Montargis on the Loing. This was completed by 1692, but the capacity of the Loing between Montargis and the Seine was insufficient to cope with the traffic generated by this and the Briare canal. Accordingly, in 1724, the Canal du Loing was completed parallel to the river and passing through Nemours to join the Seine near Fountainbleau. The great expansion in the north-west of France came later and was intimately linked with the Belgian waterway system. An early development was the opening in April 1734 of the Canal de Picardie, later to become part of the Canal de St Quentin, linking the Somme and the Oise near Chauny. Otherwise the position at the beginning of the eighteenth century was that the Sambre was navigable north-east from Maubeuge and coal was imported from Liège via the Meuse and the Sambre. The Escaut was only navigable in France between Valenciennes and Condé by 75 tonne boats, but from Condé into Belgium 150 tonne boats could pass. The Scarpe was navigable in theory from Arras, but in practice Douai was the limit. The boatmen of Arras attempted to organize themselves into a guild in 1704 to obtain privileges; but their boats were very small and the hauliers had to be in the water. The Deule was navigable above Lille on the Haute Deule and below on the Basse Deule but there was no navigable link between them, although in 1693 a link between the Scarpe at Douai and the Haute Deule at Lille had been opened. The far-sighted Sebastien de Vauban realized the need for progress in communications in the area and advocated in 1705 an improved Scarpe between Mortagne at its junction with the Escaut and Douai; a link between Valenciennes and Gravelines; a link between Douai and Bouchain by the Sensée; the completion of navigation through Lille, and of the connections between the Lys and the Aa. It was over a century before all these waterways were completed. Of those mentioned the Neuffossée Canal linking the Aa at St Omer with the Lys at Aire was completed in 1774 with a five-rise staircase lock at Arques, just south of St Omer. The traffic steadily grew on the Neuffossée Canal which formed a useful link with the coast but the staircase lock at Arques, or as it is usually known, Fontinettes, created a bottleneck. By the 1860s boats could wait for up to a week to pass through and it became the practice to allow boats to pass up and down on alternate days, thus permitting the locks to be used more intensively. Ultimately the authorities decided to install a parallel flight of locks, but this decision coincided with the opening of the English Anderton lift in 1875 in Cheshire between the Weaver and the Trent and Mersey Canal. Edwin Clark was commissioned to design a similar structure on a much larger scale at Fontinettes, which adequately dealt with the traffic problem. Each of the two tanks was capable of taking a 300 tonne Freycinet-type péniche. The lift INLAND WATERWAYS 487 worked on the same principle of counterbalancing as at Anderton by putting extra water in the tank at the upper level and so forcing the piston of the lower tank to rise, final balancing pressures being obtained by a hydraulic accumulator. The lift was opened in 1888 and continued in operation into the 1960s. Then the enlargement of the canal to cope with the increased size of barges raised questions as to the future of the lift. A new large-capacity lift was considered, but instead a large shaft lock almost on the site of the old five-lock staircase was constructed and the lift was retained as an industrial monument. Further south a very old proposal, the Canal du Charollais, now the Canal du Centre was to link the Loire south of Nevers at Digoin with the Saône to form part of a north-south link across France. This scheme was revived and work started in 1782, opening to navigation in 1793. Work also started in 1793 on the Canal de Bourgogne to link the Saône and the Yonne, again to provide a north-south connection. The French Revolution put a temporary end to most major works and it was not until Napoleon, with his vital awareness of the importance of canals, came to power that projects likely to come to fruition were again considered. In the west in Brittany, in order to stimulate industry and agriculture, a start had already been made in 1580 in making the River Vilaine navigable inland to Rennes, and in 1627 the States of Brittany approved the canalization of the Aulne between Brest and Carhaix, but the work was not pursued. In 1783 a network of canals with Rennes as the centre was proposed on the grounds that they would provide communication which would avoid the English blockade. Such canals were those linking Brest and Nantes, Pontivy and Lorient, and Rennes and St Malo. The plans lay dormant until revived by Napoleon in 1810. On 7 September 1811 stonelaying at the first lock on the Nantes-Brest Canal took place at Chateaulin but work was suspended between 1814 and 1822. It was opened in stages as lengths were finished, but it was not completed throughout until 1836. Unfortunately it was severed later by the construction of the great dam and reservoir at Guerledan. Another canal which was early considered was a link between the Loire at Decize and the Yonne at Auxerre. This, the Nivernais Canal, was started in 1784 but again the Revolution temporarily put an end to construction, delaying its opening until 1834. It is a delightful canal and forms yet another north-south link on the French canal system. One of its feeders, the Rigole d’Yonne, crosses the Yonne valley at Montreuillon over a 33m (109ft) high and 152m (502ft) long aqueduct constructed entirely in masonry and opened in 1842. East-west links were still unsatisfactory, so a major waterway, the Marne- Rhine Canal providing communication between Paris and Strasbourg and also giving access to the industrial areas of Alsace and Lorraine, was started in 1846. It passes through difficult country and is unusual in having two summit levels. The 310km (192 mile) waterway was completed in 1853. At PART THREE: TRANSPORT 488 the same time a second canal, the Aisne-Marne Canal, connected it with the industrial areas of north-east France, a connection which improved after 1881 by the construction of the Oise-Aisne Canal. Also linked with the Marne-Rhine Canal and consequential on the Franco-Prussian war of 1870– 1 was the Canal de l’Est running north on the canalized River Meuse, with an interesting short tunnel at Revin built to cut off a great loop of the river; the canal’s southern portion forms a link to Corre at the start of the navigation down the Saône to Lyons. Another modern development can be seen on the Marne-Rhine Canal. At Arzviller, a few kilometres east of Strasbourg, the canal rises through 17 locks up the Zorn valley and at the top of the flight enters a tunnel where, until recently, electric mules towed the barges through. There were considerable delays in passing the locks, so in the 1960s two new lengths of canal were built, one at the level of the canal below the lowest lock and the other at the level above the highest lock. Linking the two levels is a steep inclined plane where the barge is carried up or down transversely in a tank. The difference in level is 44.5m (146ft) and the slope is 41°. Only one tank is used but provision was made for the installation of a second should the need arise. The incline was opened for traffic on 27 January 1969. Further modernization took place on the western side of this summit in 1964 with the replacement of six locks with a single deep lock at Rechicourt. Also branching off the Marne-Rhine Canal is the Canal des Houillères de la Sarre, or the Sarre Coal Canal, suggested in 1838 when the Marne-Rhine was still under consideration. The project ran into considerable opposition but was sanctioned in 1861 when it was to be financed jointly by Prussia and France as it would benefit both countries. It was constructed between 1862 and 1866 and the first barge from Gondrexange on the Marne-Rhine Canal reached Sarreguemines on 15 May 1866. Over the years it has been gradually deepened and modernized. With the work in hand by Germany in canalizing the Saar (Sarre) to modern standards from the Moselle near Trier to Saarbrücken, this canal may prove a valuable link between the Moselle and the Strasbourg area. In the east and south the construction of the Rhône-Rhine Canal from Strasbourg via Mulhouse, with a further link to the Rhine at Basle and a short branch canal to Colmar, continuing via Besançon to the Saône north of Chalon and thence to the Rhône at Lyons, has over the years completed another vital link for north-south traffic. The first section from St Symphorien on the Saône to Dôle on the Doubs was completed in 1802. The remainder of the section between Strasbourg and the Rhône were opened as completed until the first vessel to make the full journey passed through the lock at Strasbourg on 31 December 1832. The Rhône itself has been largely tamed in this century with the construction of dams for power stations and the associated deep locks for INLAND WATERWAYS 489 barge traffic, and with the necessary improvements to the Rhône-Rhine Canal it will soon be possible for the large Rhine barges and pushtows to travel from Rotterdam to the Mediterranean at Marseilles where a new link, the Liaison Rhône-Fos, was opened in 1983 taking 4500 tonne pushtows. The Moselle has been improved with new freight handling facilities at Thionville allowing 3200 tonne pushtows to run directly to the Rhine at Koblenz, and the modernization of the Moselle at Liverdun now allows the Marne-Rhine traffic to use the canalized river instead of crossing by an aqueduct. Improvements south of Dunkirk now allow the Europa barges to serve the port and connect with the Escaut to both Belgium and central France. Finally, the river navigation of the Seine has been transformed. Although navigation from the sea to Paris and beyond has existed for centuries, until the nineteenth century it was difficult and costly partly because of the current passing bridges and partly because of low water in summer. In addition many mills had been built, both on the banks and jutting out into the river, and these caused obstructions. Despite works carried out elsewhere in France, canalization of the Seine did not begin until after 1840 when five locks and dams were built giving a depth of 1.6m (5.2ft). Twenty years later this was improved to 2m and three more locks were added. After 1910 a major reconstruction took place and the number of locks was reduced to the present total of six. Further improvement was completed with enlarged locks in 1964. An example of this development can be seen at Andresy, just below the confluence of the Oise and the Seine, where there are two small locks built in 1880, a dam and large lock 160m by 12m (525ft by 39ft) with a depth over sill of 5m (16.4ft) opened in 1959, and a new lock of 185m by 24m (607ft by 79ft) opened in 1974. This is fitted with a cylindrical sector horizontally rotating gate at the upstream end of the lock. The lock is capable of taking a 5000 tonne pushtow. All the locks below the port of Gennevilliers below Paris have now been enlarged to these dimensions. This has also allowed the development of inland ports as at Boneuil and Gennevilliers and more recently, post-1976, at Limay on the site of a former quarry. Now sea-going coasters of up to 200 tonnes as well as the usual self-propelled barges of up to 1350 tonnes can operate through to Paris. THE LOW COUNTRIES The generally flat terrain of Belgium and the Netherlands, much of it reclaimed from the sea, has been particularly favourable to the development of inland navigation, and in the north it has been considerably influenced by the extensive and complicated delta of the Rhine. PART THREE: TRANSPORT 490 Further south, in the area between Amsterdam and Rotterdam, it is true to say that the rivers and canals determine the Dutch landscape. In Roman times there were three main channels of the Rhine into the sea. One flowed to the north and entered the Ijsselmeer (Zuider Zee). The middle one, now known in its remaining stretches as the Oude Rijn (Old Rhine), entered the sea to the west of Leiden. The third, the southern branch, is the modern outlet via Rotterdam and the Hook of Holland. The Romans wished to connect the middle and southern outlets in a north-south direction and, because of the difficulty of cutting an effective channel through the inland peat, they constructed a canal lateral to the coastal sand dunes from the Old Rhine west of Leiden to the Rhine near Maassluis. This was known as the Vliet. The southern portion has disappeared, but the part between Leiden and Rijswijk still survives. Further east a more complicated route from Muiden on the Ijsselmeer using the Vecht to Utrecht joined the Lek near Gein close to where the present Merwede Canal enters the Lek. A canal was built through the centre of Utrecht in 1150 and still survives as the Oude Gracht (Old Canal). With local city and provincial power politics able to demand and purchase rights it is not surprising that yet another north-south route was developed soon after 1200. The Gouwe was constructed from near Alphen a/d Rijn on the Old Rhine southwards through Gouda to the Hollandse Ijssel and thence to the Lek. Finally in 1220–6 a lock called a spoje was installed at Spaarndam and could have been a pound lock. At this time neither Amsterdam nor Rotterdam existed. Utrecht responded by allowing its outer moat to be used for navigation, although commercial interests were against this on account of loss of trade within the city. New ports were established along the Rhine at Schiedam in 1260 and later at Delfshaven and Rotterdam with their own connections with the interior. In order to permit larger vessels to pass through without their masts fouling the superstructures of the locks, mitre gates were installed at a new lock at Spaarndam in 1567 and at a similar lock at Gouda in 1578. In the seventeenth century new canals were built specially for passenger traffic conveyed in horse-drawn boats known as trekschuiten. Between 1630 and 1660 over 650km (404 miles) of these canals were built linking city with city, though not necessarily to form a continuous waterway. Nevertheless they constituted the first internal passenger network in the world, with the boats running to a timetable and providing on many routes a frequent service which was a boon to travellers. Some routes persisted well into the railway age. Meanwhile Amsterdam was growing and needed improved transport connections with the sea. An early route was for vessels to sail east across the Zuider Zee to Kampen and then up the Ijssel past Zwolle and Deventer to join the Neder Rijn (Lower Rhine) near Arnhem. An alternative route was to sail along the coast of the Zuider Zee to Muiden and then up the Vecht to Utrecht and the Kromme (Crooked) Rijn to Wijk bij Duurstede. In time the Crooked INLAND WATERWAYS 491 Rhine silted up and a new canal was made from Utrecht to Vreeswijk known as the Vaartse Rijn or Rhine Navigation leading into the Lek by a lock built in 1284. This very early lock was 54.5m (178.8ft) long and 4.75m (15.6ft) wide. One of the early new canals for trekschuiten was the Weespertrekvaart, a canal between the Amstel at Amsterdam and the Vecht near Weesp constructed in 1638, which allowed vessels to reach the Rhine without traversing the dangerous passage across the Zuider Zee. By the beginning of the nineteenth century this had become neglected. Between 1815 and 1822 William I restored it and it was then known as the Keulse Vaart (Way to Cologne). The Lek also was silting by this time, and so a further canal, the Zederik Canal, was built from Vianen opposite Vreeswijk to Gorinchem on the Waal (otherwise the Merwede) and completed in 1825. In 1890 this canal and the Keulse Vaart south of Utrecht were improved to take 2000 tonne craft, and together they became known as the Merwede Canal. The density of traffic generated posed further problems. In 1921 more than 300 ships passed the lock at Vreeswijk on each of 29 days, and by 1930 waiting time to pass the lock could be up to twelve days. Because of these delays it was decided to construct a new Amsterdam-Rhine Canal and this was started in 1937. It involved upgrading the Merwede Canal from Amsterdam to Utrecht and then, bypassing Utrecht to the west, it followed a new alignment to Wijk bij Duurstede where it crossed the Lek on the level and continued to Tiel on the Waal. A branch, the Lek Canal from south of Utrecht to Vreeswijk, was completed in 1937 to benefit traffic travelling west to Rotterdam. The Amsterdam-Rhine Canal was opened in 1953; by the 1970s it had proved so successful that it was becoming congested and further enlargement had to be made. This was completed in 1981. The problems of crossing the Lek with pushtows were the subject of intensive studies at the Delft Hydraulics Laboratory. At both sides of the river egg-shaped basins were formed and these created whirlpool eddies keeping the main current in its bed. In this way the creation of shoals was avoided and very little dredging is required. The new massive lock structures are dramatic examples of modern canal architecture. By the late eighteenth century large ships were finding it difficult to reach Amsterdam owing to the silting of the Zuider Zee so a proposal to link Amsterdam with Den Helder, which had permanent deep water, was approved; construction started on the Noordhollandsche Canal in 1819 and its 82km (51 miles) were completed in 1825. It was not particularly successful and in 1876 it was superseded by the North Sea Canal giving a more direct route to the sea at Ijmuiden. The network of small waterways in north Holland has offered few problems to its intensive use as an integrated transport system, but with the increased size of barges against the old dimensions of bridges and locks it was necessary to improve conditions. In 1935 work started on building a new canal across . between the Massif Central to the north and the foothills of the Pyrenees to the south suggested the site for a waterway link between the Mediterranean and the Atlantic and various PART THREE: TRANSPORT 484 surveys. for oil tankers at Eastham, just below the entrance to the Ship Canal, in 1954. With the decline of the cotton industry and the changing pattern of sea transport the Manchester Ship Canal also. by Francis I in the sixteenth century, proposed a canal from the Garonne at Toulouse to the Aude and into the Mediterranean and this was the first survey of many. One of the problems was the supply