Bridges & Aqueducts

Structures of the Waterways

Last updated: 23 Sept 2021

One of the finest legacies of the waterways are the elegant bridges of cut or dressed stone. Most of the canal bridges were single-span hump-backed bridges, but there were splendid two and three-arch bridges, as well as magnificent aqueducts like the five-arched Whitworth Aqueduct that carries the Royal Canal over the River Inny in County Longford. The M50 Aqueduct was constructed in the 1990s to carry the Royal Canal over the motorway.

The Whitworth Aqueduct carrying the Royal Canal over the River Inny

Completed in 1757, the 16-arch masonry bridge at Shannonbridge is testament to the durability of 18th century engineering. The Shannon is also graced with many handsome four- and five-arch masonry bridges, most of which were constructed or upgraded during improvement works in the 1840s.

  Proposed improvements for the bridge at Shannonbridge, 1845

Accommodation bridges were built to compensate farmers who were unhappy about having their land cut in two by the waterway – the cost was charged to the canal company. Turnover bridges, like the one on the Barrow Navigation near Athy in Kildare, allowed horses towing boats to cross from one side of a canal to the other without disconnecting from its harness.

A number of rolling lift bascule bridges straddle the Royal Canal, including the wrought-iron Scherzer bridges where it meets the Liffey in Dublin’s Docklands.

​John Binns, a director of both the Grand Canal and the Royal Canal, has the unique distinction of lending his name to a bridge on both waterways.

Often adorned with plaques stating their name and date of construction, many canal bridges were named after directors or major shareholders. John Binns, a director of both the Grand Canal and the Royal Canal, has the unique distinction of lending his name to a bridge on both waterways.

Hamilton Bridge in Dublin was originally called Broome Bridge, but it was renamed for Sir William Rowan Hamilton, an eminent mathematician who hurriedly carved                 i2 = j2 = k2 = ijk = −1 onto the bridge wall with a penknife when the equation unexpectedly came to him as he strolled the Royal Canal on his way to Dunsink Observatory. With that historic formula, he pioneered the discovery of quaternions.

Plaque on Hamilton Bridge, Royal Canal

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