Thomas Telford was a Smart Guy

There are smart guys all along the narrowboat canal, but the smartest one was Thomas Telford, the Scottish lad who engineered the parts of the canal that we’ve run on.  Some context is in order. Telford died in 1834, or about two years after the Rideau Canal was opened here in Canada.  Various parts of the Shropshire Union Canal were built and running commercial traffic before work even started on the Rideau Canal in 1826.

We’ve explained earlier why there are so many canals in the UK:  Canals were the superhighways of their day, lugging large quantities of goods from place to place as horse drawn wagons could only pull a limited quantity of something a short distance on the unimproved roads of the day: A horse-drawn narrowboat could regularly ship 20 to 30 tons of something along the canals simply because a floating boat has almost no friction.  It isn’t fast, but it makes up for the lack of velocity with the increase in capacity.

Telford started out as a stonemason’s apprentice at the age of 14, learning how to bash rocks, then through various contacts in London became an engineer and surveyor eventually winding up in Shropshire. In 1790 he built his first Iron bridge, iron being the modern building marvel of the day, much as we look at carbon-fiber today.  

Telford was a bit of a maverick in that he tested things.  Would this kind of casting in this dimension, stand up to this kind of load?  We are talking before super computers. Telford’s tools were paper, pencil, perhaps a rudimentary slide rule and keen observation with a nimble mind.  Victorian-era high technology.

On our trip we got to try out a few pieces of his craft, the top three being the Chirk Aqueduct, the Chirk Tunnel and the Pontcysyllte Aqueduct.  You could argue that almost all of the canal system we traveled from Wrenbury to Llangollen was his work and you might not be far from wrong, but we’ve picked the more impressive pieces.

The problem with canals is water doesn’t run uphill very well.  The idea behind the canal is to have the least number of locks on a route that is not always a straight line from one place to another.  

Where it gets complicated is the land.

Unless you’re on a perfectly flat geography, there will be things that get in the way like rivers, valleys, hills, towns and fields. To change heights or to detour around things like rapids and waterfalls with a 30 ton load of slate or coal on a horse-drawn boat takes some engineering.  Locks work and in the day that was the choice. Wales, however, is hilly and there is no escaping it.

The River Dee cut a swath through the route for the canal, making things difficult.  If Telford had done locks there would have been at least a dozen, six down the valley, a short canal, then another six back up to where the canal would run, essentially a staircase on either side and at least a day or more to pass going up and down in 20 foot increments.  

An aqueduct was a wiser choice. It took ten years to build the stonework and put a cast iron canal trough on the top of aqueduct, to allow boats to pass in 20 minutes, instead of a full day. Telford then did the same thing at Chirk, not quite as long, or as high as Pontcysyllte, but the same concept of an aqueduct topped with a navigable canal.  In between? The Chirk Tunnel, 460 yards of hard work, lined by bricks containing the waterway and the towpath to pull the narrowboats through.

Crossing the Pontcysyllte and Chirk Aqueducts is a marvel.  There is a fenced walkway on one side, the former towpath for horses, but the other side is a sheer drop to the valley below.  We’ve included still photos for now, as the real-time video shot in high-def is too large for WordPress.  We’ll add links to a Youtube source later so you can see the whole thing as we transit.

A fun aside, on the outgoing trip a charming couple said they had never crossed the Pontcysyllte on a boat and could they come along?  There was plenty of room on the tiller deck so Rob had company on the journey as they marveled at the view and thanked us profusely for our hospitality when we made the other end.

Today, the whole area is a UNESCO World Heritage Site and a very impressive memorial to the days when engineers used their minds and hands to solve problems.  Thank you, Thomas Telford.