The Open Door Web Site : History : The Industrial Revolution : The Development of Canals in Britain : John Rennie

By the 1790's Britain was going through a period known as "Canal Mania". During this time Acts of Parliament were passed for the construction of over 50 canals.

Canals were built mostly as a method of carrying either heavy goods, such as coal, iron and brick, or for the transport of delicate products, such as glass and china. Josiah Wedgwood, a Midlands pottery manufacturer, integrated his factories with canals so that it was possible to ship his unique, blue and white pottery all over Britain. This avoided transporting delicate china pottery over badly made, and very bumpy, roads. Many potteries were established in the same region of the country and this area of Britain became known as "The Potteries".

Some products, such as fresh dairy produce which needed to get to market quickly, also used canal transport. For this type of product the canal boats which were used were faster because they were pulled by more than one horse.

Most of the canals were deliberately constructed to be narrow for both economic and technical reasons. The wider the canal, the more expensive it was to build and the more difficult it became to solve construction problems, such as the water supply, lock building and tunnel building.

Because the canals were built individually, not following any central plan, they tended to be of different widths. The wooden boats were built to a variety of sizes, with widths varying from 4 metres to 6 metres. Consequently, canal barges, or "narrow boats" as they were called, were not always able to move freely around the canal system, unless they had been built to the smallest design.

The narrow boat was usually a little over 2 metres wide and between 17 and 23 metres long. It was pulled along the canal, usually by a horse, at a speed of 3 to 5 kilometres per hour. Each boat only needed one horse and one boatman to operate it, which made it an economical form of transport. The major drawback was that it was very slow. Most narrow boats were run by a family crew. The husband, his wife and their children all lived in a small cabin, measuring 3m by 2m, at the rear of the boat.

Normally, a canal boat was pulled by a horse which was attached to the boat by a long rope. The horse walked along the tow path on one side of the canal. When the boat came to a canal tunnel, the horse was walked over the hill, and the narrow boat was "legged" through the tunnel. This meant that two men would lie on their backs on planks of wood on the boat. They would then push the boat by "walking" their feet along the roof and walls of the tunnel.

John Rennie (1761-1821)

Rennie, John (1761 - 1821)
Print Artist: Jan Pieter Waterloo, 1790-1861
Engraving
Image credits:
http://www.sil.si.edu/

John Rennie was a Scottish civil engineer who moved to London after his graduation from Edinburgh University. He started his working life as a millwright and he made his name improving mill machinery by introducing iron parts. Rennie moved on to Boulton and Watt's Albion Mill where he designed and constructed machinery, once again extending the use of iron for the machine parts, such as the gears.

In the 1790's, Rennie worked on the Kennet and Avon canal as well as on a canal construction in Rochdale, Lancashire. By 1800, he was employed on a project to drain the Lincolnshire fens. During the early part of the 19th century, Rennie also worked on the construction of London's East India docks as well as the naval dockyards in Plymouth and Portsmouth.

Perhaps Rennie's most famous works were three of London's bridges across the Thames. He built the original Waterloo and Southwark bridges. His New London bridge was completed by his son in 1831. This bridge was bought by an American oil company in 1968 and can now be seen at Lake Havana in Arizona.

The canal builders had to overcome many technical construction problems. These included building a canal over a hill, across a valley or through a mountain. The canals were also known as navigations, and the men who worked long and hard to construct them were known as navigators, or "navvies". The navvies were armed with a pick, a shovel, a wheelbarrow and gunpowder. They were responsible for building the huge canal network and, later, the railway network.

The canal was first surveyed along a route which was kept as level as possible. Where the canal needed to climb up or down a hill, a system of locks was used. The canal was dug out along the surveyed route and the channel was plastered with specially prepared "puddled clay". This clay had been mixed and stirred into a plaster which resembled mud and this formed a waterproof layer for the water to run over. The canal was filled by feeder streams which often had to be diverted over a long distance. Water shortage was a problem with many canals during the summer, and, in winter, the canals would often freeze solid. Both of these factors made the canals unusable during certain periods of the year.

The locks were stone, brick or even iron constructions. Each lock had water-tight gates at either end. When the narrow boat entered on one level, the gates were closed. Then, depending on whether the boat was going up or down, the lock was either filled with or emptied of water, until the water levels in the lock and in the canal were the same. The gates were then opened, and the boat continued on its way. If the canal climbed a long hill, then the locks were built in sequence and were called "staircase locks".

By 1800, there were over 6000 kilometres of canals in Britain. However, forty years later, canals were in decline in the face of a new and faster rival, the railways.