Peter Mark Roget (1779 - 1869) By the age of fourteen Roget was studying medicine at Edinburgh University, graduating five years later to tutor the children of a wealthy merchant from Manchester. From 1808-40 he concentrated on medicine, paying particular attention to the senses. During this time, in 1814, he also invented what he called a 'log-log' slide rule to calculate the roots and powers of numbers. This formed the basis of slide rules that were common currency in schools and universities until the age of the calculator over 150 years later. He was elected a Fellow of the Royal Society the following year. In 1824 he wrote a paper describing an optical illusion he had noticed while watching the wheels of a horse drawn carriage through the blinds of a window. The illusion - 'the Persistence of Vision' - allows us to see a succession of still images as a continuous, moving picture, and it is this that makes cinema and television work. Roget studied the phenomenon with a simple device he built himself. When he set it running very slowly the tiny part of a spoke that was visible through a vertical slot was a moving point but, as its speed increased, he began to see the whole spoke. Moreover, the spokes - in reality perfectly straight - appeared curved and, with the exception of the two vertical spokes, they all curved downward. He simplified the system by using a single slit and a single spoke and traced the part of the spoke visible through the slit. It described a curve exactly the same as he had seen when looking at the carriage wheels. At that moment he realised that if the slit moves fast enough, the previous image of a single section of the spoke will still be on the retina as the next segment comes into view. If the speed is sufficiently high, an image of the whole - curved - spoke can be created. Roget did virtually no more work on the persistence of vision after this paper, but it immediately sparked off a surge of inventions. The most simple of these was the Thaumascope, a piece of card with a picture on each side. If rotated fast enough, the two pictures merged into one. Before the end of the century, Louis Le Prince had made the first, primitive moving pictures of traffic over a bridge in Leeds, and ultimately these inventions led to motion pictures and the birth of cinema seventy-five years later. In 1848 he retired from his position as Secretary of the Royal Society, a position he had held since 1827 and embarked on the project that has made his name, Roget's Thesaurus of English Words and Phrases. As early as 1805 he had compiled, for his own personal use, a small indexed catalogue of words which he used to enhance his prolific writing. When he retired he picked this up and published the first edition in 1852. A book of synonyms with 990 classes of words that allowed easy access to words of similar meanings, it has never since been out of print. Articles * Victorian Studio Photographs Multimedia Zone * Great Victorian Achievements Animation Historic Figures * Sir Isaac Newton Timelines