
 Hamilton, William Rowan (18051865) 
  Hamilton did early work on caustic curves and was led from this to his discovery of the law of least action, which enabled many physical problems to be expressed more elegantly. 
  The idea for quaternions came to Hamilton suddenly on Oct. 16, 1843, while he was standing on Brougham ("Broom") Bridge, where Broombridge Street crosses the Royal Canal, Dublin; a plaque under the bridge, on the towpath, was unveiled by the Taoiseach (head of the Irish parliament), Eamon De Valera, on Nov. 13, 1958. 
  Hamilton's interest in complex numbers was stimulated by his friend and compatriot John Graves, who pointed Hamilton in the direction of John Warren's A Treatise on the Geometrical Representation of the Square Root of Negative Quantities. 
 www.daviddarling.info /encyclopedia/H/Hamilton.html (807 words) 
