Peter Mark Roget

 Jan. 18 is the birth anniversary ...

"...of physician and philologist Peter Mark Roget, born in London in 1779. He was a physician, trained at the University of Edinburgh, and he helped to found the University of London as well as a medical school at the University of Manchester. He was also a Fellow of the Royal Society, served as its secretary for over 20 years, and invented a slide rule that was widely used until the invention of the pocket calculator. He was interested in optics, and published a paper in 1824 called "Explanation of an Optical Deception in the Appearance of the Spokes of a Wheel Seen Through Vertical Apertures." He was the first to notice something called "persistence of vision" — the illusion of movement when looking at a series of still photographs in rapid succession — which formed the basis for future motion picture technology.

He was 61 years old, and had just retired from his medical practice, when he decided to devote his retirement to publishing a system of classifying words into groups based on their meanings. Other scholars had published books of synonyms before, but Roget wanted to assemble something more comprehensive. He said, “[The book will be] a collection of the words it contains and of the idiomatic combinations peculiar to it, arranged, not in alphabetical order as they are in a Dictionary, but according to the ideas which they express.”

He organized all the words into six categories: Abstract Relations, Space, Matter, Intellect, Volition, Sentient and Moral Powers. And within each category, there were many subcategories. The project took him more than 10 years, but he finally published his Thesaurus of English Words and Phrases in 1852. He chose the word “thesaurus” because it means “treasury” in Greek.

Roget’s Thesaurus might have been considered an intellectual curiosity, except that at the last minute Roget decided to include an index. That index, which helped readers find synonyms, made the book into one of the most popular reference books of all time. It is considered one of the great lexicographical achievements in the history of the English language, and it has been helping English students pad their vocabularies for more than 150 years

Roget's Thesaurus of English Words and Phrases Classified and Arranged so as to Facilitate the Expression of Ideas and Assist in Literary Composition has been in print continuously since its publication in 1852.