I looked into his history and found that his education was in medicine and his work on the thesaurus was part of a lifelong coping mechanism to fight depression. But before he actually got around to publishing his great book, he not only invented the slide rule scale, but following the death of Sir John Hershell, Roget was secretary of the Royal Society from 1827 to 1848. He also made observations in sight and persistance of vision that influenced the development of movies.
From"Cheshire Antiquities,© Craig Thornber, Cheshire, England, UK.
"His observations were based initially on looking at the world through a series of slits such as one might have in a vertical Venetian blind or pallisade. A rotating cartwheel viewed through such as system gives an optical illusion. The spokes at the top and bottom appear straight but those at the sides appear to bend downwards. Roget worked out the path of the light to show how this happened. He went on to explain a phenomenon that often perplexes devotees of Westerns, a hundred years before the invention of film. At certain speeds, the cartwheel appears to stop or go backwards. Roget's observations were made by viewing through vertical slits but he showed the position of each spoke in the wheel at each glimpse and how this could lead to the optical illusion of stasis or backward motion. The same phenomenon is observed when a film is made with a cine camera. In 1820, Roget worked with Michael Faraday and Joseph Plateau in a series of experiments on vision leading to Roget's paper to the Royal Society on the Persistence of Vision. Roget's work showed that an image persists in human perception for about one sixteenth of a second and this forms the basis on which animations, film and television are based. "
On 9 December 1824, Roget presented a paper entitled Explanation of an optical deception in the appearance of the spokes of a wheel when seen through vertical apertures. ...
While Roget's explanation of the illusion was probably wrong, his consideration of the illusion of motion was an important point in the history of film, and probably influenced the development of the Thaumatrope, the Phenakistiscope and the Zoetrope.
He also was involved in the creation of University of London and the precursor to the Royal Medical Society. A busy Guy...
While I was searching this out, I came across the fact that the invention of the Ln scale (for finding e^x) was by an 11th grade high school student.
From a post by Robert Adams:
The Ln scale was invented by a high school student, Stephen B. Cohen, in 1958. The original intent was to allow the user to select an exponent (in the range 0 to 2.3) on the Ln scale and read e^x on the C (or D) scale and e^(-x) on the CI (or DI) scale. Pickett and Eckel were given exclusive rights to the scale in the early sixties. Later, Stephen Cohen created a set of "marks" on the Ln scale to extend the range beyond the 2.3 limit, but Pickett never incorporated these marks on any of their slide rules.
And just one more footnote, I always found it a little quirky that the log scale on the slide rule was linear.