Notes on Canal History and Engineering

Canals and canal engineering from ancient times to the present


Contents

  1. Varieties of Canals and Their History
    1. Ship Canals
    2. Ancient Canals
    3. Chinese Canals
    4. European Canals
    5. American Canals
  2. Sources of Information
  3. Canal Engineering
    1. The Water Budget and Puddling
    2. Locks
    3. Location
    4. Canals and Railways
    5. Inclined Planes
    6. Towage
    7. Canal Difficulties

Varieties of Canals and Their History

I mean by canal an artificial channel for navigation. Canals were also built for drainage, water supply, and ornament. Canals are distinguished from natural watercourses by containing slack, or stagnant, water with no obvious current. Inland navigation can take place on natural watercourses (rivers and lakes), artificial slack-water canals, or on channels of an intermediate nature, such as an improved river.

I want to discuss in this article the different kinds of canals that have existed, in order to make clear the significance of the canals of the Industrial Revolution, which are those that have been most familiar. Then, I will suggest some sources of information, and end with some notes on elementary canal engineering, which is usually slighted in economic and social histories. My purposes are to inform the person who may not have thought much about canals in the past, but has now become interested, and to give some knowledge of canals to those chiefly concerned with other matters on which canals have a bearing.

Ship Canals

Today, canals are mainly relatively short routes for large ocean-going ships leading to coastal ports, such as the Houston Ship Channel, or protected ways bordering the shore, such as the Intracoastal Waterway around the Gulf of Mexico and up the east coast of the United States that connects lagoons behind barrier islands. The Panama Canal (1904) and the Suez Canal (1869), which opened important shortcuts, are restricted by the size of their locks, but still see use. The Manchester Ship Canal (1894) is now a pleasure waterway, too small for ocean ships, but more importantly no one has any reason to send ships up to Manchester any more, or for that matter even up to London. These modern facilities are rather boring, anyway.

Even today there is a proposal for a canal across the Kra isthmus in Thailand, a shortcut between the Indian Ocean and the South China Sea, mainly for oil tankers to and from Japan (Sunday Times, 9 January 2000). The article says it would save 180 000 per voyage, and would only cost 13 billion. If money is at 5%, this would mean 10 ships per day just to pay the interest charges, if all the savings were paid directly to the canal, which, of course, they would not be. The expense would be a direct subsidy to the shippers. Only public enterprise, or more precisely corporate exploitation of public enterprise, would attempt such a doubtful investment. The French suggested the canal after they had dug the Suez, but Britain interfered, which it has no power to do at present. [The Times article says the Foreign Office could no longer 'proscribe' to the Thais. Spellcheckers cannot save those of limited vocabulary from embarrassment.]

Ancient Canals

Canals existed in ancient times. There were canals in Babylon, both for irrigation and for navigation, and canals connected the Tigris and the Euphrates. However, Egypt led in early canals. The commerce of Lower Egypt (the delta) was mainly by canal; roads were very unimportant, and wheels rare in this rich and early civilization. The Egyptians are said to have had 80 canals, up to 100 miles long. The most famous was the Grand Canal from the Nile to the Red Sea, said by Herodotus to have been dug by Necos, son of Psammetichus (25th dynasty), but Strabo says the canal was built by Sesostris much earlier, so that Necos only restored it. Darius is said to have worked on the canal, but it was certainly restored by Ptolemy II and operated during classical times. It was 37 miles long, from Arsinoë on the Bitter Lakes to the Red Sea, 100 ft wide, and 40 ft deep, according to Pliny. Trajan cleansed and restored the canal, but it fell into disuse, merchants carrying their goods overland from Berenice with a 3-days' journey. About 635, in the Caliphate of Omar, it was restored by Amru, Governor of Egypt, but then fell into permanent disuse. Sluices or half locks were used on Egyptian canals. The Mediterranean-Red Sea canal had one at its Mediterranean end at Arsinoë

There were repeated attempts to dig a canal across the isthmus of Corinth to save the long journey around the Peleponnesus, by Demetrius Poliorcetes, Caesar, Nero and Caligula. This project failed more from the opposition of those whose businesses would be ruined by it than on account of engineering difficulties. There was, remarkably, a portage railway here from about 600 BC until the 9th century AD. The Roman general Drusus (1st century) built a canal connecting the Rhine and the Ijssel in Holland. Most of the Roman Empire was not appropriate for canals, but they were built wherever they were practicable and needed. One of these canals, the Fossdyke, between the River Trent and the River Witham near Lincoln in England, still exists (but not in Roman form, of course). It was restored by Henry I. It is 11 miles long, and on a single level. The Caerdyke, a 40-mile canal from the Nene at Peterborough to Lincoln, may also have been a Roman canal, built under Domitian. Rome, in fact, was later served by a large inland port made artificially, and connected with the sea by a canal, not the unreliable Tiber and the earlier port of Ostia.

Chinese Canals

Commerce in China followed the great rivers, of which the greatest were the Huang-Ho and Yangtze, navigable for 2400 miles and 2900 miles, respectively, from their mouths on the eastern coast. The Yun-Ho, or Grand Canal, ran for over 800 miles (Needham gives 1035 miles, Peking to Hangchow, and a summit of 138 ft) from Hangchow to Tientsin, crossing these rivers, and eliminating the dangerous sea passages between the principal cities. Of its three divisions, the oldest connected the two great rivers, and was, according to Confucius, completed in 486 BC, during his lifetime. It was repaired and enlarged in the 3rd century AD (Han dynasty). The southern division, from the Hang Chow bay to the Yangtze, was built in the 7th century AD, and the northern division, from the Huang-Ho to Tientsin on the Pei-Ho, which gave communication with Peking, 350 miles upstream, was constructed in 1280-1283, during the early Yüan (Mongol) dynasty. The Yun-Ho was more an artificial river than slack-water canal, fed by rivers and lakes, and with currents, especially in the central division, that hindered northward movement. Its primary function was the transport of tribute grain from the South to Peking.

Depths of 7 ft to 11 ft were maintained by 75 barrages, or sluices, across the canal. Plank sluices, that could be fully or partially closed by a gate made from separate planks were introduced around 605-618 AD. Boats were hauled upstream through the waterfalls over differences of elevation of 20 ft to 30 ft by windlasses, or by main force of gangs of men with ropes. The canal was often wider than 100 ft, but sometimes only 50 ft. The banks were protected by stone in many places, and stone bridges were built across it. The route crossed the great alluvial plain of eastern China, well inland. The boats were moved mainly by mast and sail, or oars. Smaller boats were pulled by gangs of men. The northern division used mainly existing rivers and lagoons. It was troubled by lack of water, and the Pei-Ho froze from November to March, so it declined and was eventually used only by local traffic, except for the annual rice tribute to Peking.

On other canals, the Chinese used inclined planes faced with stone on which boats were dragged from one canal level to another by men pulling on ropes. Inclined planes were not used on the Grand Canal, apparently because the Emperor's long warships would break when leaving a plane. J. Needham would very much like to make the pound lock a Chinese invention of about AD 1000, but the case he argues is very weak (Vol. 4, part 3, Sec. 28), resting solely on the interpretation of a literary text. He must explain the lack of any later use of pound locks, since there were none when Western contact was made, and he gives no illustrations. If there ever was an early Chinese pound lock, it was a sport and had no consequences. The Grand Canal sank to a very low state in the early 20th century, but has been restored.

European Canals

Early French canals were also built to connect river navigations. The first modern canal was the Briare-Montargis canal connecting the Seine and Loire, begun by Henri IV and completed by Richelieu in the reign of Louis XIII. It had 42 locks. The Orleans canal between the same rivers was begun in 1675 and completed during the minority of Louis XV, with 20 locks. The Picardy canal connected the Somme and the Oise. But the greatest French canal was the Languedoc Canal, or Canal du Midi, from the Atlantic to the Mediterranean across southern France, built 1666-1681, but first proposed under Francois I. It went from the Garonne near Toulouse to the Lac de Tau near Sète, 180 miles long, with 114 locks. There was a notable flight of 8 locks near Béziers, as well as a tunnel there 720 ft long lined with freestone, the first bored for navigation. The channel was 144 ft wide and 6 ft deep, sometimes carried in aqueducts on high bridges over rivers. The summit level, with 600 ft elevation at Narouse, was supplied from a reservoir and aqueduct at St Ferriol receiving its water from La Montaigne Noire. Francis Riquet was the engineer, and Colbert the minister. Its example stimulated the building of other European canals, possibly including the Duke of Bridgewater's canal of 1757.

Transport in Russia was long dominated by its great rivers. Peter the Great, in the early 17th century, began a program to connect the rivers by canals to integrate the system. The Kiel Canal was constructed in 1777-1785 in what was then Denmark to eliminate the long and difficult passage around Jutland between the North and Baltic Seas. This canal originally had 6 locks 27 ft by 100 ft that could take ships of up to 120 tons. The channel was 100 ft wide at the top, 54 ft at the bottom, and was 10 ft deep. This canal has now been transformed into a ship canal, of course.

The first canal in England, the Exeter Canal, was dug in 1564-1566 to bypass a difficult river estuary, and used the first pound locks in Britain. These are not the locks now surviving, but those that were on the original small canal. The first recorded pound lock was built on the Brenta near Padua in 1488. A pound lock was used a bit later at the junction of two canals in Milan whose levels differed by 34 feet. This is an invention that could very well have been made in Roman times if there had been the necessity. The preservation of ancient engineering works is so incomplete that the absence of an example does not prove the pound lock was not known then. The pound lock with mitre gates was first regularly used in France in the mid-16th century.

Sir Richard Western (1591-1652) built the Wey Navigation between the Thames at Weybridge and Guildford. In the 15 miles, there were 7 miles of artificial cut, 10 locks and 4 weirs. The fall to the Thames was 86 ft. This navigation was opened in 1653 (concurrently with the first turnpike Acts), and is a typical river improvement of the time. John Hadly opened the Aire and Calder navigation from Weeland to Leeds and Wakefield in 1703, which Smeaton extended to Halifax in 1764. A similar project was envisioned for the Sankey Brook to St Helens, but Henry Berry (1720-1812) ran his 10-mile Sankey Canal beside the river, but independently of it. This canal, with a drop of 78 ft, was built 1755-57. The canal gradually liberated itself from the natural waterway, and began to strike out on its own.

The first modern canal is generally regarded as the Duke of Bridgewater's canal from the Worseley mines to the Mersey at Runcorn, via Manchester, engineered by James Brindley (1716-1772). It was on one level from Worsley to Runcorn, with a flight of locks at the latter point to descend to river level. It had the remarkable Barton Aqueduct over the Irwell, and considerable embankments, so it represented a new level of engineering. Here Brindley first used puddling, an indispensable aid to canal construction, according to Rees. Brindley also engineered the Trent and Mersey Canal, with the posthumous Harecastle Tunnel (1792).

What most people fascinated by canals mean by a canal is the remarkable network of broad and narrow canals and improved rivers that put every point in lowland Britain within 15 miles of navigable water, and was an essential part of the Industrial Revolution, which coincided with the Canal Age, 1760-1840. These canals made possible the general supply of coal, which was power to industry and life to the poor. Not only coal, but stone, iron and copper ores, lime, sand, manure, and agricultural produce, which earlier could not support the cost of transport, moved freely. Later, fly boats on regular schedules that moved night and day carried general merchandise, and here and there even passengers.

This wonderful system was rendered completely unnecessary by railways after 1840, but survived or only slowly decayed into the 20th century for peculiar and remarkable reasons, and has now in large part been transformed into a system for pleasure cruising in small boats following the utter loss of any commercial traffic after the 1960's. The pleasant appearance of an earlier age has been well-preserved, and it forms one of Britain's unique amenities. First railway companies, and then the government, have been induced to provide the financial support for this survival of earlier days.

American Canals

The United States was admirably suited for navigation on its coastal and river waters, and this was by far the most important means of transport until the railways, made especially effective by the introduction of steamboats around 1810. There were early ambitious schemes to open up shortcuts and routes to the interior by digging canals. The most important were the canals from the Chesapeake to the Delaware to connect Baltimore and Philadelphia, from the Susquehanna to the Delaware to give inland Pennsylvania an outlet to Philadelphia, between the Tioga, a tributary of the Susquehanna, and the Allegheny, giving a route to the Ohio, from Lake Ontario to the Delaware and so to Philadelphia, from Presque Isle on Lake Erie to the Allegheny River and thence to the Ohio, plus a branch up the Kiskeminetas and a short portage to the Juniata, a tributary of the Susquehanna. Also George Washington's pet project, making the Potomac navigable up to Cumberland, and perhaps even beyond to the Ohio.

Virginia and Maryland passed Acts in 1785 to make the Potomac navigable by building locks at Great and Little Falls, with channel improvements at Seneca Falls and Shenandoah Falls to remove the rapids there, and to open communication with Cumberland. This was expected to be done by 1790. As it turned out, the 185-mile canal was not completed until 1850, after a new start in 1828, and the railway reached Cumberland first. Phillips reports in 1803 that the Chesapeake and Delaware canal was 'now cutting.' The 14-mile canal did not carry traffic until 1829, after a new start. From 1919 it has been a sea-level channel without locks. Similar fates awaited all the grand schemes just mentioned. Most were never begun, others were abandoned before completion, and a very few were finished only after railways had rendered them obsolete. The reasons for this almost complete failure were the lack of a capable engineering profession, and the dearth of capital.

Phillips' 1803 account of American canals does not include a successful canal that was already in service, the Middlesex canal between Boston and Lowell, opened in 1795, and engineered by Loammi Baldwin, nor any hint of the first really successful American major canal, the Erie Canal, built and operated by the State of New York. Governor De Witt Clinton solved the problems of American canals by having a corps of engineers trained in England, and by attracting British capital to American investments. Robert Fulton (1765-1815), who introduced steamboats to America, may have been instrumental in this decision, since he returned to the United States in 1806, having spent twenty years as a canal engineer in England. The engineers of the Erie Canal furnished the nucleus of the American engineering profession, not the useless graduates of West Point, and English money later built the railways of the United States. The Erie Canal was the only profitable canal ever built in the United States, where canals were almost exclusively, and remain, heavily subsidised and little-used government enterprises. It has long been replaced by the now almost unused but very costly New York State Barge Canal. There are no relics of the original canal.

The building of canals on the British model began only simultaneously with railway building in the 1830's, and followed the old paths of commerce, not the new developing ones. These canals, in Ohio, Indiana and Illinois, were opened as late as the 1850's, when railways had been well-developed, and closed soon after. They were poorly built, and suffered from profiteering and corruption, which was endemic. They were filled in and almost completely forgotten by the 1870's. There are no preserved canals in the United States as in Britain (relics of the Chesapeake and Ohio canal, which never got near the Ohio, can be seen near Washington, DC, however. It is part of the National Capital Parks System).

The bare fact is, that even a minimal single-track railway has much greater capacity and flexibility than a small-boat canal, and is more cheaply operated and maintained. When British railway companies discouraged traffic on the canals that they came to acquire, the effect was simply to replace obsolete facilities by better ones for the general good. At present, road transport has superseded all other forms of inland transport of goods, whether by water, rail or air. The reason for this is not entirely technological superiority (though the direct connection of source and destination without intermediate handling is very important), but related to political, business and social considerations. The user has control of his own business, not subject to the inconveniences of dealing with an arrogant third party or a helpless victim of irrelevant labour struggles. He need not pay directly for the heavily subsidised necessary facilities, except those immediately employed in carriage.

Sources of Information

Diderot and d'Alembert's Encyclopédie of 1763 has a good contemporary article on canals, including a detailed description of how a lock works. Abraham Rees' The Cyclopaedia of 1819 (Vol VI) has a lengthy article on canals that is practically a handbook of canal engineering with detailed treatments of all its aspects. There is not only a history of canals (owing a lot to the Encyclopédie), but also a description of British canals, river navigations, and railways at the height of the Canal Age. It may be difficult to find, but I very highly recommend it as a first-hand account of canal engineering. Rees recommends John Phillips's General History of Inland Navigation as a comprehensive reference, which gives details of American canals on p. 571ff. He also mentions Robert Fulton's Treatise on Canal Navigation of 1796, in which Fulton suggests the construction of small canals (tub-boat canals) as economical. William Chapman's Observations on the Various Systems of Canal Navigation (1797) treats inclined planes, small-boat canals, and Chinese canals. The Phillips and Chapman books have been reprinted by David and Charles. Adam Smith in Wealth of Nations (1776) is quoted with regard to the benefits of canals, in which one horse does the work of 30 on the turnpike, or one man the work of three with 18 horses on the turnpike. Smith reckons a canal as economic at 20 times the cost of a turnpike, although often cheaper to construct in fact.

To learn about Britain's canals, one should begin with Hadfield's British Canals, 8th ed., revised by Joseph Boughey (Stroud, Gloucs.: Alan Sutton Publ. Ltd., 1994). Charles Hadfield, a driving force in canal preservation and a master historian, published the first edition in 1950 (he was half of David & Charles), and the book has remained the best one-volume account of English, Irish and Scottish canals from the beginning of the Canal Age up to the present. Visits to the canal museums in London, Stoke Bruerne, Foxton, and many other places will give one an excellent appreciation of the canal and its culture. There is a great deal of specialist canal history and cruising enthusiast material available. It is actually easier to see relics of the Canal Age in context than it is to see equivalent railway relics, which all reflect a much more recent era.

The Kennet and Avon canal is easily seen today from trains between Newbury and Pewsey. Just before reaching Newbury, the entrance to the canal from the Kennet Navigation can be observed. At Crofton, just west of Great Bedwyn, the pump house with its chimney (now restored) can be seen to the west, and the reservoir to the east. Both portals of the Savernake tunnel are visible, the east portal on the south side of the track, the west on the north side. The Grand Junction canal can be seen at many points on a journey from Euston to Rugby. Both are broad canals, engineered by Jessop and Rennie.

The Canal Age deserves careful study by the railway historian, since railways took advantage of the business arrangements already developed for canals, such as Parliamentary Acts, as well as of its engineering, in earthworks, tunnelling and bridging. The Canal Age is largely responsible for the creation of the professional Civil Engineer, capable of managing large and innovative projects on scientific principles, replacing the largely self-taught millwright, mason, carpenter, mine viewer and other craftsmen. An excellent biography of an outstanding engineer of the Canal Age is: Charles Hadfield and A. W. Skempton, William Jessop, Engineer (Newton Abbot: David and Charles, 1979).

Canal Engineering

Until the latter years of the Canal Age, all construction and maintenance was accomplished by the labour of men and animals, and all design was empirical, in the same way as had been done since Roman times. Only in the 19th century were steam engines used to pump water, or for motive power. This must constantly be kept in mind when considering 18th-century engineering and its remarkable achievements.

The Water Budget and Puddling

Canals may appear much simpler to engineer than they actually are, something that the unprepared promoter continually discovered in the Canal Age. The two most important requirements are: (1) an adequate supply of water for the summit level, and (2) the canal must hold water and not leak. Both of these requirements are almost automatically met for sea-level canals in wet areas of high water table. They are with the greatest difficulty met for a canal that strikes out cross-country and ascends hills. Let us discuss these requirements first, since they influence everything else.

Every canal has a water budget. Water is lost by leakage and evaporation, and with every boat that passes a lock. This water is generally supplied from the summit level of the canal. The summit level can be supplied naturally by runoff from precipitation, or artificially by pumping. All available streams to supply a summit reservoir must be gauged, and the reservoir must be large enough to even out the cycles of supply and consumption. The supply of the summit level is the most important factor in canal design. If the summit level is made higher to avoid tunnelling, water supply becomes more difficult. If the summit level is made lower to avoid water problems, the canal may be more circuitous or involve much tunnelling. The canal itself must be rigorously separated from natural waters because of their variability.

On the Kennet and Avon canal, Rennie planned a long summit tunnel at Savernake, but Jessop convinced him to raise the summit elevation to shorten the tunnel, and to supply the necessary water by steam pumping at Crofton. A canal could bring coal, making steam pumping quite feasible. The reservoir to supply the pump is still to be seen, as is the pump house and pump. The railway passes between the pump house and the canal, and runs directly over the tunnel, whose eastern portal is easily visible to the south of the track.

One of the secrets to making a canal hold water is the use of puddling. This does not mean slathering on a layer of clay and letting it dry, like some kind of mortar. Strong clay, in fact, is useless for puddling, since it absorbs great quantities of water, then cracks on drying out. Topsoil is equally useless, since not only do plant roots in it decay, but earthworms chew it and moles eat holes in it. Puddle is a compacted semiliquid mixture of loamy subsoil and coarse sand or fine gravel (which renders it unpalatable) . Suitable puddling-stuff is worked with a spade, adding the correct limited amount of water, until it is homogeneous. This mixture is quite impermeable to water, but must never be allowed to dry out.

Puddle is used to separate the water of a canal from porous strata, and is placed in ditches to prevent water from spreading away from the canal, and to stablilize embankments. Any embankment must be treated as a porous stratum, and puddle ditches are required on both sides down to the water table. Canals may be lined with puddle when necessary. With a railway, the earth must only have sufficient bearing capacity, and some permeability is a definite asset. With a canal, the nature of the canal bed is much more significant, and must be carefully studied by the engineer.

Locks

The pound lock is an essential feature of cross-country canals. Without it, there would never be enough water to maintain the navigation. A natural stream, with a considerable flow, can be made navigable by building sluices or half-locks to divide the river into approximate levels and raising the water level sufficiently to allow boats to pass. These can be permanently open, or can be shut to conserve water and opened only when a boat desires to pass. The Thames, for example, had such sluices to a very late date, the boats being pulled through upstream by a winch and rope. A closed half-lock raised the water level enough that it could be used to power a mill, and the miller had to be paid for the lost water, or flash, that he gave to a navigator. Boats ascending the Severn to Gloucester had to tarry at shoals until the tide arrived to carry them over. Occasionally, the violence of the tide (the Bore) increased the dangers of navigation.

The pound lock consists of a chamber, the pound, that can be filled or emptied as desired so that the water level coincides with either the lower or the higher water levels of the reaches to either side of it. A sea lock can match the current height of the tide. The ends of the pound are closed off by water-tight gates that can be opened to admit a boat. These gates are mitred so that water pressure holds them tightly shut when the levels are different on the two sides. Water passages are made from the upper reach to the lock chamber, and from the lock chamber to the lower reach, with a gate, called a paddle, that is raised or lowered by a rack and pinion to open or close the passages. Openings can be made in the lower lock gates instead of in the chamber wall.

The procedure for passing a boat from the upper to the lower reach is as follows. The gates are closed, and the upper paddle is opened. When the chamber has filled to the level of the upper reach, the upper gates can be opened and the boat can enter the lock chamber. Then the upper gates, and the upper paddle are closed, and the lower paddle is raised to empty the lock into the lower reach. The boat sinks as the water is removed, until the water level is the same as that of the lower reach. Now the lower gates can be opened, and the boat can pass into the lower reach.

A boat that enters the lock from the lower reach sees the breast wall of the lock before it. The boat must be stopped before it strikes the breast wall, and damages it. A bumping-piece is provided to protect the breast wall. The gates are similarly defended from the canal boat. The breast wall and gate frames are often built on sturdy pile foundations.

The lock chamber is made as small as practicable, to save water. This also limits the capacity of the boats that can be used, so there is a trade-off. Another way to save water was by means of a side pond. When emptying a lock, the first half of the water is run off into the side pond, not into the lower reach. If the next boat passes upstream, the first half of the lockful of water can be drawn from the side pond. The amount of water used per boat is halved. An equivalent method is to duplicate the locks, using one for ascent and the other for descent, so one can serve as side pond to the other. The amount of water required for the passage of one boat is determined by the largest lock, so the rise of the locks on a canal is made as uniform as possible.

The distinction between a 'broad' and a 'narrow' canal is in the size of the locks. The locks of a narrow canal will take one narrow boat, about 7 ft wide, while those of a broad canal will take a boat 14 ft wide (or more), or two narrow boats side by side. Away from the locks, the canals were wider to allow boats to pass easily, and perhaps to turn.

Location

Rees' description of the proper method for establishing the route of a canal already resembles very closely the later accepted practice for locating a railway. He emphasises the importance of a careful assessment of possible traffic and revenues by the engineer. This, more than any other fact, shows why the profession of engineer had to be created to handle such projects rationally. The engineer has the knowledge and experience to manage the complete project, not simply one of its parts, however important individually, as was earlier within the limited purview of the millwright or mason. This effective means of management was well-developed when it was required for the building of railways. The creation of the modern profession of Civil Engineer is the greatest gift of the Canal Age to the Railway Age. In modern times, this lesson is apparently being forgotten, as large projects are more in the hands of lawyers and accountants who only know how to cream off profits, and are ignorant of the essential technical details. Engineers are again reduced to the status of hired workmen.

When it comes to the detailed location, Rees recommends starting with the summit level, deciding its location and length, and assuring the supply of water. A long and low summit level makes water supply and operation easier, but may involve deep cuttings and long tunnels. A short and high summit level is faster and cheaper to construct, but at the expense of added lockage and difficult water supply. Rennie favoured long summit levels, but Jessop knew that this meant extra expense and delay in opening, so he favoured higher summit levels, which seems to have proved the better engineering choice. At each end of the summit level, at least two locks are recommended, a suitable distance apart but still close enough to be supervised by a single lockkeeper. It was economical to concentrate locks at a single location. The Duke of Bridgewater's canal, for example, was on a single level up to the flight of locks at Runcorn than led down to the Mersey. Rennie's unsuccessful Grand Western Canal was also mainly a single level, with inclined planes on its eastern end instead of locks. The long level of the Leeds and Liverpool canal between Skipton and Bingley, with the Bingley 5-rise staircase at its eastern end is another of many possible examples. This tendency survived into early railway engineering most distinctly, in the form of overcoming elevation by inclined planes, especially in the United States. It was always considered good practice to concentrate heavy gradients on one locomotive division, since the maximum gradient determined the weight of the trains, however short it might be.

Several times Rees mentions the importance of taking levels with a 'spirit level fitted with a telescope' in surveying a canal. The earliest American canals failed because of inaccurate levels, but the presence of English engineers with their telescopic levels demonstrated the necessity of careful work. There seems not to have been a single telescopic level or theodolite in the United States in 1800; land surveying was done exclusively with compass and chain, and there was no profession of Civil Engineer there until after the Erie Canal. Railways, even more than canals, demanded accurate surveying instruments.

A canal can either follow the contours of the land, or can strike out in a straight line. If it follow the contours, only slight earthworks will be necessary and there will be a minimum of lockage, but the route will be long and devious. A straight line demands heavy and expensive earthworks, and often much lockage. At the beginning of the Canal Age, there was little experience in tunnelling and major earthworks, so canals tended to follow the contours or have frequent locks. The northern end of the Oxford canal is a typical example. The Grand Junction canal locked down into the valley of the Ouse, then locked back up again, and the high aqueduct was never built. Tunnels required a long time for completion, and were often temporarily bypassed with tramway links. Later canals, like the main line of the Shropshire Union, were straight and level wherever possible, since by this time earthworks were much easier to construct. There was a little late improvement of canals by straightening and elimination of locks, but most canals remained as they were built.

Rees also mentions the desirability of a balance in the amounts of cutting and embankment, so that excess material will not have to be piled, or pits left where fill was removed. On narrow canals, turning basins and passing places must be provided, and sufficiently frequently that no boat would have to be backed to a point where two boats could pass one another. One should compare the sizes of lock chambers with the width of the canal.

Bridges were another necessity, for roads that crossed the canal, to provide connections between lands severed by the canal, and for the towpath to cross to the other side. It was suggested at first that paved fords would do, and these are much cheaper than stone bridges. However, the maximum depth of water in a ford could be only 2' 9", governed by the sizes of farm carts, so this expedient was seldom used. Rotating or swing bridges on roller bearings could be moved out of the way of canal traffic. These seemed to be more popular in England than lifting bridges. Bridges were built of stone, brick, or cast iron. The Chinese had stone pedestrian bridges over canals, elliptical arches with long axis vertical and crossed by steps.

Canals and Railways

Rees contemplates canals, rivers and railways as forming 'one great compound and connected System of Inland Communication' [italics his] even at this date, and gives particulars of railways along with those of canals in his survey. As early as 1819, therefore, railways were very well known and common adjuncts to canals. He gives the origin of railways as the wooden railways of Tyneside in 1680. He subjects them to the same discipline of rational location and traffic estimation as canals, and again recommends 'spirit levels with telescopic sights' for their layout.

Railways (what would now be called tramways or plateways) were used as branches and extensions of canals to mines in the hills, as means of overcoming heights without worrying about water, for access to traffic not sufficient to warrant the cost of a canal, and to bypass points where construction would be difficult or expensive, at least temporarily. The Lancaster canal was in two parts, connected by a railway, for example. The Crompton and High Peak Railway, though not constructed until later, was projected to connect the Peak Forest Canal with the Cromford Canal and form a trans-pennine route.

A Gloucester Railway was proposed in 1804 to connect the Sodbury coal mines in Gloucestershire with the Avon at Bitton, below Bath, and eventually with the Kennet and Avon canal. The mines at Worsley on the Bridgewater Canal were reached directly by water, since the canal even penetrated into the mine. This was quite unusual, of course.

Rees gives the usual gauge of railways as 4 feet, a figure supported by much other evidence. When steam railways arrived, the general tendency was to increase the track gauge, first to 4' 8-1/2", the wider gauge of Tyneside, then to 5', 5' 3", 5' 6" and finally to Brunel's 7'. There was no other significance to what became 'standard gauge' and it was never widespread previously. It was simply Stephenson's arbitrary choice, not a survival of any tradition, especially not of the gauge of Roman wagon wheels. For more information on tramways, see Tramway Engineering

Inclined Planes

It is evident from Rees that inclined planes are a well-known element, and simply a kind of railway that is operated by rope haulage. The power can be men or animals, water wheel, a counterbalance caisson that can be filled and emptied, a steam engine, or by the weight of descending loads, controlled by a brake wheel at the top of the incline (self-acting or gravity). Inclines overcome elevation in a limited horizontal distance. A vertical lift is simply an inclined plane taken to an extreme. Boats can be lifted bodily, as in China, but more usually in wheeled cradles or water-filled chambers. Sometimes boats could be separated into sections for this process.

One of the most fascinating uses of inclined planes in connection with canals appeared at the end of the Canal Age with the State of Pennsylvania's Main Line of Public Works (1834), between Philadelphia and Pittsburgh across the Allegheny Mountains. This system, proposed in the early 1820's as an answer to the Erie Canal, used steam railways and inclined planes operated by stationary engines to connect long canal segments, which were the principal component. See my web page on William Strickand for full details of the Main Line, which was successfully operated for twenty years. Enthusiasm for railways eclipsed it completely. It was neary totally forgotten by 1876, and is still not properly appreciated by historians. The Morris Canal between the Hudson and the Delaware used planes with boat lifts, and the Delaware and Hudson Canal between the same rivers used a gravity railway to serve its mines in the Lackawanna Valley.

There were many inclined planes in England, on the Stockton and Darlington, for example, as well as in Cornwall and in Shropshire. The Middleton Colliery, near Leeds, had an incline famous for being worked by Blenkinsop's cog-wheel engines, although it was later worked in self-acting form in which empty wagons were drawn up by the loaded wagons and controlled by a large brake wheel at the top of the incline. The first railway signal (in a sense) was erected here to show when the empties had been attached to the rope, and the loads could be permitted to descend. Of course, this had nothing to do with later railway signals.

A certain Mr Barnes, a coal viewer of Bywell on Tyneside, constructed a self-acting plane 864 yd long, rising 144 yd vertically. The counterweight, a plummet, weighed 16 cwt 2 qr. A loaded wagon could descend in 2 minutes and 30 seconds. The plummet, descending in a well, would then draw the empty waggon back to the top of the incline.

Towage

River barges were usually towed by gangs of men in the exercise known as 'bow haulage' from the bows that the men seized. Towpaths could not easily be provided across the private land bordering rivers (though the tow gangs had right of way) and men were better able to deal with the conditions of the banks than animals.

Canal boats were sometimes towed by men, but more usually by a horse, mule, or pair of donkeys accompanied by a driver (usually a boy) on a towpath provided by the canal company on its own property. The single towpath made the passing of two boats an event in which one tow rope had to be passed over the other. Only later were some canals provided with two towpaths, which made the operation simple. At an overbridge where the towpath changed sides the tow rope had to be disconnected. This also had to be done when the towpath did not pass through the arch of a bridge.

There were often no towpaths in tunnels. Instead, the boats were propelled by men pressing against the top or sides with their feet. Sometimes men known as 'leggers' hired themselves out for this service.

There were early attempts to apply steam propulsion to canals, but steam never supplanted animal towage generally, until finally both were replaced by Diesel boats after about 1900. Steam towage gradually took over on the more important navigations (those which had retained some traffic) after about 1860. The main drawbacks to steam power were the large space required for the boiler, and the restrictions on speed necessary to prevent damage to the canal banks.

Canal Difficulties

People who expect trains to be on time and run every day would be sorely vexed by canal operations. There were sufficient human problems, such as boats going only when full, slow movement, danger to lock-keepers in lonely places, pilferage and other inconveniences well treated in social histories, but there were also problems of a more physical nature. The most important were water problems, either too little or too much. The droughts of summer could leave insufficient water for navigation, especially on summit levels, and drying out of the canal structure could damage the puddling and make cracks allowing what little water there was to escape. The floods of winter could wash away embankments, cover locks and make access difficult. If the water froze, navigation was definitely over. Even in Britain, this occasionally caused problems, but in places like the United States it was a regular occurrence. The uncertainty of canal traffic forced users to keep larger stocks than than they would have done otherwise, and necessitated the provision of warehouses, which are frequently seen at canal ports.

There were a few cases of successful passenger operations on canals, such as the Paisley - Glasgow fly boats, but in general canals were an unpleasant way to travel, since they were very slow, and the passengers were at the mercy of concessionaires for food and accommodation. Some boats stopped overnight, like stage coaches, while others travelled night and day. For more information on canal services, social histories should be consulted.


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Composed by J. B. Calvert
Created 17 February 2000
Last revised 21 July 2000