Sir, - Permit me to comment on the article about William Rowan Hamilton and Broome Bridge by Fintan Gibney (Science Today, July 19th). The mathematical work which brought Hamilton, while still an undergraduate, to the notice of the Dublin intelligensia was a long paper on geometrical optics entitled Account of a Theory of Systems of Rays, which he presented to the Royal Irish Academy in April 1827, at the age of 21. It had grown out of a previous paper (1824), On Caustics.
His predictil crystals and its experiment on of conical refraction in biaxiaal verification by Humphrey Lloyd were made in 1832 and led three years later to the award of the Royal Medal of the Royal Society and a knighthood. It was hailed as a striking confirmation of the wave theory of light.
Hamilton himself considered his invention of quaternions at Broome Bridge on October 16th, 1843, to have been his greatest achievement. Broome Bridge is named after William Broome, a director of the Royal Canal Company who lived nearby (see North Dublin, by Dillon Cosgrave, 1909).
Hamilton's whimsical custom of referring to the bridge as "Brougham Bridge" may have been due to his attitude to Lord Henry Brougham (1778-1868), the great Whig politician and defender of the particle theory of light. Lord Brougham is also remembered for a type of one-horse closed carriage which was first made for him. - Yours, etc.,
Dr Ian Elliott, Kilternan, Dublin 18.