Person: Wallace, William
William Wallace worked on geometry and discovered the (socalled) Simson line of a triangle.
Mathematical Profile (Excerpt):
 Although he was not a student, Wallace did attend mathematics classes at Edinburgh University and both Robison and Playfair encouraged the young man who they realised had very considerable mathematical talents.
 At this time Wallace began to publish mathematics and his first paper appeared in the Proceedings of the Royal Society of Edinburgh in 1796.
 Playfair advised Wallace to apply for the post of professor at the Royal Military College at Great Marlow which became vacant in 1803, and one year after he was appointed there he was joined by Ivory.
 Thomas Leybourn's Mathematical Repository was produced by the staff at the Royal Military College and Wallace soon joined in contributing articles.
 Candidates for the vacant chair included Wallace, Haldane (who was professor at St Andrews) and Charles Babbage.
 Wallace had an impressive collection of testimonials including ones written by Playfair, Dugald Stewart, Maskelyne, Charles Hutton, William Herschel and Maseres.
 In a straight vote between Wallace and Haldane, Wallace was appointed by 18 votes to 10.
 This really annoyed Leslie who now regretted that he had supported Wallace over Haldane and even regretted resigning the mathematics chair himself.
 Wallace's work was on geometry and Simson's line (which is definitely not due to Simson!) appears first in a paper of Wallace in 1799.
 In this Encyclopaedia Britannica article Wallace uses Newton's notation, but in his article Fluxions for the Edinburgh Encyclopaedia which was published in 1815 he used Leibniz's differential notation and was therefore the first to write an English treatise on the calculus using differential notation.
 Wallace also invented the pantograph, an instrument for duplicating a geometric shape at a reduced or enlarged scale.
 As a Professor, Wallace was regarded as an able teacher, he was popular alike with pupils and colleagues.
 Wallace retired from his chair at Edinburgh in 1838 due to ill health.
Born 23 September 1768, Dysart, Fife, Scotland. Died 28 April 1843, Edinburgh, Scotland.
View full biography at MacTutor
Tags relevant for this person:
Astronomy, Origin Scotland
Thank you to the contributors under CC BYSA 4.0!
 Github:

 nonGithub:
 @JJO'Connor
 @EFRobertson
References
Adapted from other CC BYSA 4.0 Sources:
 Oâ€™Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive