2005 was designated the UNESCO World Year of Physics and in Ireland this year has been designated ‘Hamilton Year 2005: Celebrating Irish Science’. The coin celebrates the life of Sir William Rowan Hamilton, Ireland’s greatest mathematician and scientist. Renowned as one of the world’s greatest ever mathematicians, he spent his entire life in the environs of Dublin. Born at midnight on the 3rd / 4th August 1805 in Dublin, he was educated by his uncle, James Hamilton, an Anglican priest. His genius was apparent at an early age. By the age of five he had already learned Latin, Greek and Hebrew and at the age of thirteen he could speak 13 languages. His pursuit of learning continued throughout his life. He studied and excelled at both classics and science at Trinity College, Dublin and at the age of twenty-one he was appointed Andrews’ Professor of Astronomy to the University of Dublin and Royal Astronomer of Ireland. Hamilton’s work in the fields of optics and dynamics theory was rewarded with gold medals from The Royal Society of London and The Royal Irish Academy. Hamiltonian dynamics is important for almost every advanced physical science, and forms only part of his work that enlightened the world. His later work focused on pure mathematics and, in 1843, his mastery over symbols and mathematical language enabled him to solve a long-standing complex algebra problem. While walking along the Royal Canal in Dublin, on his way to the Royal Irish Academy, he devised the concept of ‘Quaternions’ and carved his formula into the nearby Brougham Bridge (now called Broom Bridge) where a plaque now honours the discovery. The reverse of the coin pays tribute to Sir William Rowan Hamilton’s use of algebraic equations that revolutionised mathematical physics. His understanding of symbols and mathematical language is represented by a decorative circular pattern formed from these symbols. At its centre is the Nabla, the symbolic operator introduced by Sir William to represent any arbitrary function. The symbol is so called because of its visual resemblance to the Egyptian harp of the same name. This beautiful silver €10 coin is an elegant testament to the work of Sir William Rowan Hamilton.