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.
Thomas Telford arguably created the most impressive cast-iron structure, the Pontcysyllte Aqueduct 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.
The Bingley Five-Rise Locks were drained in 2012 for repair work, allowing visitors a glimpse into the construction and design of the staircase locks
Early canals slavishly followed natural contours, avoiding great spans, and as a consequence meandered. As engineers gained knowledge they began to use locks to quickly gain and lose elevation. Soon they were conquering considerable changes in elevation via staircase locks, such as the Bingley Five-Rise Locks on the Leeds & Liverpool Canal, which climbs 59 feet over a distance of 320 feet.
America also has a rich history of canals, but as in Britain the canals declined as railroads expanded. Nevertheless, you can still travel US canals, including the Erie and the Chesapeake & Ohio canals.
Although canals were a considerable gamble, rarely being completed in time and always over budget, they could return substantial profits once completed and could cut transit times from weeks to days. Canal mania set in during the 1790s, especially as England was at war with France. Being able to move goods around England and Wales without braving French warships and the weather of the English Channel was a considerable incentive. (It’s interesting that Britain caught the canal mania from the French.)
Soon various canal companies were crisscrossing the country, joining London to Bristol, Bristol to Birmingham, Liverpool to Manchester and Liverpool to Leeds. There was no coordination to these schemes, except possibly through the process of obtaining a royal assent to build a canal. Almost every canal was built by private enterprise but somehow the haphazard process resulted in a waterway infrastructure that fostered the Industrial Revolution. Soon every sort of manufacturer had easy access to a canal. In Wales, slate miners and lime producers could use the Llangollen branch to connect to the Shropshire Union Canal and from there to the rest of England. Cadbury Chocolate even built a model factory town alongside the Worcester & Birmingham Canal at Bournville. Josiah Wedgwood built his Etruria pottery business alongside the Trent & Mersey Canal, taking advantage of the narrowboat’s gentle ride to ensure his wares reached their destination undamaged.