Survey Data

Reg No




Categories of Special Interest

Architectural, Historical, Social, Technical

Original Use



1785 - 1850


313200, 237172

Date Recorded


Date Updated



Two-arch limestone canal bridge of c.1790 and railway bridge of c.1845, carrying Broombridge Road on north-south axis over Royal Canal (north) and Dublin-Sligo railway line (south). Random coursed squared calp limestone walls with shallow piers flanking each arch having limestone ashlar plat-band to base of parapets and limestone ashlar coping. Elliptical arch to train bridge has rusticated limestone ashlar voussoirs and skewed squared calp soffit. Round arch to canal bridge has tooled limestone voussoirs and keystone with squared calp soffit. Canal bridge has Portland limestone plaque to northwest spandrel with inscription commemorating formula for quaternions devised by William Rowan Hamilton. Rubble stone embankment walls to either end have stacked coping. Break in east parapet provides access to steel footbridge to Broombridge Station. Tarmac carriageway follows steep gradient to both north and south approaches.


Named after William Broome, a director of the Royal Canal Company. The canal section of the bridge is no doubt the older structure. It is of considerable significance for its associations with William Rowan Hamilton who. on the 16th October 1843, inscribed his mathematical formula for quaternions on to the bridge when out walking with his wife. The plaque under the bridge was unveiled by the Taoiseach √Čamon de Valera, himself a mathematician and student of quaternions,on 13th November 1958. The railway bridge probably dates from the 1840s, while the two crossings now form a most appealing historic structure in the landscape at a junction of public transport and public amenity.