THIS week sees the start of celebrations to mark the 200th anniversary of the towering Pontcysyllte Aqueduct. Thomas Telford's engineering triumph near Llangollen is said to be one of the wonders of the Welsh waterways. On Wednesday TV science expert Dan Cruickshank will explain the problems overcome by Telford to create the 126ft high bridge across the Dee Valley. Sponsored by the Institution of Civil Engineers - Telford was its first president from 1820 until his death in 1834 - the illustrated talk forms part of Wrexham's Science Week. Other events are planned throughout the coming months, culminating with a stunning firework display and re-enactment ceremony on November 26, 200 years to the day when the aqueduct first opened. Jon Griffiths, British Waterways Wales and border counties general manager, said: "The Pontcysyllte Aqueduct was a truly amazing structure when it was constructed and still rightfully earns its place as one of the seven wonders of the waterways. "It remains the longest and highest navigable cast iron aqueduct in the world and is a testament to the vision and skill of the engineers who built it. Two centuries later, instead of carrying industrial cargoes, it attracts thousands of tourists and boaters from all over the world who come to enjoy this landmark structure." Steve Bayley, chief economic development officer with Wrexham council, said: "The bicentenary celebrations will not only commemorate a major civil engineering feat of the industrial revolution, but will raise the profile of the aqueduct as a proposed world heritage site." The 1,007ft long aqueduct, which towers 126ft over the Dee Valley on the Welsh border, was built by Telford and and fellow canal engineer William Jessop. They came up with the idea of using an iron trough, sealed with Welsh flannel boiled in sugar, plus an ox-blood mortar. The structure in a scheduled ancient monument. Every year it is crossed by 10,000 boats and more than 25,000 walkers. It was drained and completely refurbished in 2003 in preparation for the celebrations, as part of a £2.15m overhaul. British Waterways and its partners have also invested in new and upgraded facilities and environmental improvements in the area, including a new 32-berth mooring basin at Llangollen. And at Trevor Basin, which opens on to the northern end of the aqueduct, there are new paths, landscaping, seating, artwork and interpretation boards. carlbutler@dailypost.co.uk | 
