{"id":480,"date":"2016-01-23T22:11:00","date_gmt":"2016-01-23T22:11:00","guid":{"rendered":"http:\/\/narrowboatingforbeginners.com\/wordpress\/?page_id=480"},"modified":"2017-12-06T19:51:28","modified_gmt":"2017-12-06T19:51:28","slug":"canal-history","status":"publish","type":"page","link":"http:\/\/narrowboatingforbeginners.com\/wordpress\/canal-history\/","title":{"rendered":"Canal history"},"content":{"rendered":"

\"Shadow<\/a><\/p>\n

C<\/span>anals are a link to the past, a look to the future, either cutting edge or outdated almost the day a canal was completed. The canal system was fueled by the early days of the Industrial Revolution when the steam engine was an incredibly inefficient machine, useful only for pumping water out of coal mines.<\/p>\n

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The dizzying view from a boat crossing the Pontcysyllte Aqueduct in Wales.<\/figcaption><\/figure>\n

The canal mania began in a time when wealthy landowners were consolidating their fields under the Enclosure Act, denying common grazing land rights that had been observed for centuries. Displaced farmworkers moved to the cities, further fueling the Industrial Revolution, which needed a way to get coal, potteries, alkalis and timber to the cities and factories.<\/p>\n

Canals were a response to the simple need to get raw materials to manufacturers and finished goods to market. They were a natural outgrowth of the use of rivers, then improvements to those rivers to make them into navigations and finally true canals.<\/p>\n

They came into being when someone realized that on land a horse can pull a wheeled cart several times its weight, but it can pull a boat fifty times its weight over water. What\u2019s more, the horse can pull that weight for longer distances and at a constant speed\u2014it didn\u2019t need to vary for delicate porcelain or raw iron ore.<\/p>\n

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Construction<\/h2>\n<\/div>\n

For the most part the canals didn\u2019t require advanced technology. Instead most canals were dug by hand, using pick axes, shovels and wheelbarrows to dig and remove material. Gunpowder was occasionally used for blasting tunnels, but hand tools still did most of the work.<\/p>\n

Clay was used to line the first \u201ctrue\u201d English canal, the Bridgewater, but there were skeptics who had argued the plan literally wouldn\u2019t hold water. James Brindley showed a Parliamentary committee it would work when he built a watertight trough with puddled clay in Whitehall in front of lawmakers. Restored canals are now lined with polyvinyl chloride and concrete, but puddled clay (clay mixed with water) tamped down by passing cattle worked for a century or more.<\/p>\n

Many of the aqueduct and lock chambers were made of local stone, although apparently John Rennie regretted that when building the Avoncliff Aqueduct<\/span><\/a>. The local stone cracked in the frost and has needed to be repaired several times. Rennie got it right, however, when he built the nearby Dundas Aqueduct<\/span><\/a>.<\/p>\n

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Rennie had great success using cast iron, which was a relatively new structural material, having first been used in the 1770s for the Ironbridge that crosses the River Severn in Shropshire. Rennie used cast iron for several bridges, including the Southwark over the Thames in London.<\/p>\n

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One of the pillboxes along the Kennet & Avon Canal<\/figcaption><\/figure>\n

Thomas Telford arguably created the most impressive cast-iron structure, the Pontcysyllte Aqueduct<\/span><\/a> over the River Dee in Wales. The cast-iron trough is more than a thousand feet long and more than a hundred feet above the river valley. The trough rests on eighteen masonry piers held together with mortar that includes water, lime and oxblood. The cast iron trough is joined by strips of Welsh flannel dipped in boiling sugar and covered in molten lead. It remains today largely as Telford originally designed it.<\/p>\n