Engineering


 


How the canals were planned


When the first canals were planned, usually a group of rich men, maybe land owners or factory owners, came together. They hoped that the project would improve travel and trade in their areas as well as making them a good profit. Before the canals were built a route had to be planned. The company had to get a Bill through parliament first.
The people who decided where the canal should go were the engineers. In England there were three famous engineers who worked on canals: Brindley, Telford and Jessop.
Some people objected to the building of canals. Mill owners, for example, objected because the building of the canals meant that their mills would lose water. Farmers, whose grain was ground in these mills, also objected. People who were involved in road transport and coastal shipping objected because they would lose money if the canal companies succeeded in transporting goods in this new way.
Other buildings went up along the banks of the canal. The companies had to build lockkeepers cottages, warehouses, stables and workshops. Many of these buildings can still be seen today.

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Navvies
Navvies are teams of men who moved from constructing one canal to another. They did this in the same way as labourers do today on new motorways. In the 1790's there were about 60,000 men working on canals all over the country. The word navvy is short for navigation. That word was first used to describe these canal workmen whose work was hard, tiring and often dangerous. They had to dig out the earth with a pick and shovel and then they had to wheel it away in a barrow. When some of the canal had been complete, water could be let in from nearby streams and rivers. When canals were being built there were many accidents. Rarely were there any doctors to help people who were hurt.

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Puddling
Before water could be let in, the canal had to be made waterproof.
This was done by puddling. The puddling was a mixture of loam and
clay which were spread on the bottom and on the sides of the canal.
This was then trampled down to a thickness of about 30 centimetres.
It then formed a watertight seal. Most canals built over 200 years
ago have remained intact since the puddle was first laid.

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Locks
The lock is the building most often associated with the canal. In layman's language, it is like the steps in a staircase which take boats up and downhill. Here is an example of a lock made by John, one of the boys in 5th class.

 

Click here for demonstration of how canal locks operate

Click here for an Interactive Canal Locks Demonstration





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Aqueduct
Aqueducts are like tunnels and are a way of taking a canal across a change of level, usually a river or a deep gorge. The people who built the first aqueducts were the Romans. They built aqueducts before the canal age. In the canal age aqueducts were needed especially where a series of locks would have been difficult to build and would also have been slow to travel through. The first aqueduct built in Britain were built at Barton on the Bridgewater Canal. The big advance in aqueduct engineering came when they built cast iron troughs. (The trough is what the water runs through.) Up until then, troughs were made of stone and the water ran through a channel of earth and puddle clay.
One of the most famous aqueducts in the world is the Pontcysylite Aqueduct in Wales. If you look closely at the photograph you will see a horse pulling a barge across it. This aqueduct is thirty six metres high and has seventeen arches. To imagine how high this is, it is probably close to the height of the round tower in the village of Clondalkin, Co. Dublin. This aqueduct was built in Wales by two famous engineers, Jessop and Telford.
It is important that aqueducts are repaired and maintained on a regular basis. Today they are built of steel and reinforced concrete. The greatest danger facing them is the cold weather. If thick ice forms in the trough. It expands and this causes cracks in the structure and a risk to the trough. To reduce the risk of an accident, some of the water can be let out of the aqueduct. Many of them have a series of plugs, just like giant bath plugs. To release the water in the troughs, a number of the plugs can be pulled. This allows the water to crash down into the valley below.
The Barton Aqueduct in England has a tank which can hold 800 tonnes of water. This aqueduct can swing to one side from the centre. It may need to do this when large ships need to pass underneath. There are parallel gates across each end of the tank which can rise or fall to let water in or to empty the water, each time the aqueduct has to be moved.

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Mr. Browne's 5th class provided the information for this page.