On October 16 in 1843, one of science's great "flashes of genius" strikes mathematician William Rowan Hamilton, 38, as he walks along Royal Canal to Dublin, Ireland. In an instant he sees the solution to a problem he has been working on for 10 years, that of algebraically dissecting three-dimensional space. He has invented the theory of quaternions, a landmark in the development of algebra. Hamilton etches the fundamental formula of quaternions into the stonework of Brougham Bridge, before he can get to his desk.
—from The Illustrated Almanac of Science, Technology, and Invention