Peter Mark Roget

Peter Mark Roget (b. Jan. 18, 1779, London, Eng.--d. Sept. 12, 1869, West Malvern, Worcestershire), English physician, philologist, and scientist.

Widely remembered for his Thesaurus of English Words and Phrases (1852), a comprehensive classification of synonyms or verbal equivalents that is still popular in modern editions. Roget theorized in 1824 that the retina of the eye retains an image for a fraction of a second until the image changes. This persistence of vision theory is to fool the eye into believing a succession of separate and slightly different images to be actually one moving image. In 1852, Roget's persistence of vision theory had inspired others to exploited inventions that animated pictures. Franz von Uchatius, a German, put an animated strip of a drawing (done on glass) into a lantern and projected the resulting moving images onto a movie screen. Germans called this animation process, "The magic lantern."

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. Roget concentrated on medicine from 1808-1840. Roget primary medical research was in the field of human senses. In 1814, he also invented what he called a "log-log." Roget's invention is what as known to today as a slide rule to calculate the roots and powers of numbers. This formed the basis of slide rules that were common in schools and universities, until the calculator age over 150 years later. In 1815, the Royal Society elected Roget as an official fellow.

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 persistence of Vision allows us to see a succession of still images as a continuous moving picture. This 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 speed increased, he began to see the whole spoke.

Moreover, the spokes in reality were perfectly straight. Spokes 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. Spoke had curved the same as he had seen when looking at the carriage wheels. At that moment, he realized that if the slit moves fast enough, the previous image of a single section of the spoke would still be on the retina as the next segment comes into view. If the speed were sufficiently high, an image of the completely curved spoke would 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.

In 1848, he retired from his position as Secretary of the Royal Society, a position he had