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Montgomeryshire Canal
  When water crosses water  

One of the most dramatic features of many canals is the aqueduct, where canals are carried over rivers or valleys.
The ones on the Montgomeryshire Canal are not large, but they still caused problems in Victorian times because they leaked and almost collapsed !
The largest crossing is over the River Vyrnwy near the English border at Llanymynech, with 5 arches over the river and 3 arches over the nearby flood plain. It partly collapsed not long after it was first built because of the enormous weight of the thick layers of puddled clay used as a waterproof lining to hold the water.

On the Ellesmere Canal there is an amazing aqueduct 37m (121ft) high and 307m (1007ft) long which crosses the River Dee.
This is the Pontcysyllte Aqueduct, designed by Thomas Telford and completed in
the cast-iron
metalwork was
added to
strengthen the
Vyrnwy Aqueduct
This aqueduct needed emergency repairs several times over the years. Cast-iron tie bars (metal rods passing right through from side to side and fixed with bolts) and reinforcing beams were attached in 1892 to prevent it from splitting apart.
  The Berriew Aqueduct over the River Rhiw, seen below, also had to be repaired, and the bolted ends of tie-bars can be seen on the photograph below right.  

seen from
above and
Berriew Aqueduct Berriew Aqueduct

Smaller aqueducts on the canal used cast-iron "U" shaped troughs bolted together, and these had fewer problems. This was the method used by the famous engineer Thomas Telford for his towering aqueduct over the River Dee - see the box at top right of this page.

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