On 16 October 1843, Hamilton, the greatest Irish mathematician of all time, dis- covered the numbers called Quaternions. He had been trying to work out the problem of multiplying points in three dimensions for several years and the solution came to him in a flash as he was walking with his wife by the Royal Canal in Cabra.

"It had got to the stage with him when his children would be asking him every morning, 'can you do it yet?'" says Dr Richard Watson of NUI Maynooth (NUIM). "So when he got the flash of inspiration while walking on Broom Bridge, he carved the formula into the stone to commemorate it."

Hamilton's discovery is only the third recorded flash of inspiration in the world . . . the others being Archimedes' 'Eureka!' discovery in the bath, and Frenchman Poincerre's discovery while stepping off a bus. While Ham- ilton's carving of the Quaternions formula i2 = j2 = k2 = ijk = -1 is no longer visible on the bridge, a plaque was unveiled by the then Taoiseach Eamon De Valera in 1958.

However, there is some confusion about Broom Bridge's name. "Newspaper reports from 1958 clearly say that De Valera had renamed it Hamilton Bridge, " said Watson. "But whether this was ever undertaken by Dublin City Council is unclear. Either way, the name Hamilton Bridge never caught on and I don't suppose it ever will now."

This Tuesday, as part of Maths Week, a large group of people will make the annual walk from Dunsink Observatory in Finglas, where Hamilton worked, to Broom Bridge to commemorate the 164th anniversary of the mathematician's discovery. Nobel prize-winner for physics, Frank Wilczek, will also be taking part.

"Hamilton's discovery was quite a breakthrough at the time and really shocked the maths world when they realised how powerful it was, " says Dr Fiacre O Cairbre of NUIM, who is organising the event. "He became known as the Liberator of Algebra and to this day, Quaternions are still important."

In fact, films such as Lara Croft: Tomb Raider and The Matrix Reloaded were created through the use of Quaternions by animators. "He really is Ireland's greatest mathematician and the annual walk is our way of commemorating his work, " said O Cairbre.

'The Hamilton Walk' takes place this Tuesday at 2pm. Anyone wishing to take part should contact Dr Fiacre O Cairbre on (01)708 3763 to book a free place