**Duncan Liddel** was a Scottish mathematician, physician and astronomer who lectured on mathematics and astronomy on the continent. He made several endowments to Marischal College, Aberdeen.

- Before we continue with Liddel's biography, all his publications appear to be in medicine with none in mathematics.
- Liddel wanted to make a career in mathematics, but that, like many others before him, he failed to do so, and turned instead (or, as well) to medicine - which was always, by strong contrast with mathematics, a reliable way to earn a steady, and often lucrative, income.
- Liddel's polymathy, in short, can be seen as the result of necessity rather than as the untrammelled ranging of an ambitious free spirit.
- After studying at King's College, Aberdeen, Liddel appears to have been uncertain as to what career he should follow and, in 1579, he left Scotland and travelled to Frankfurt an der Oder, now known as Frankfurt (Oder) a town in Germany close to the Polish border.
- By the time that Liddel went there, it had been reformed along the lines of Wittenberg University.
- There Liddel met fellow Scot, John Craig who influenced him greatly so we should give brief details of John Craig (who must not be confused with the John Craig who has a biography in this archive).
- By October 1579, when Liddel arrived at Frankfurt an der Oder, Wittich was back in Wrocław where he worked with Andreas Dudith.
- Craig taught Liddel mathematics, philosophy and medicine.
- If Liddel had been unsure of what he should do before meeting Craig, there is no doubt that he was quickly convinced by Craig that mathematics was the subject for him.
- When Craig was preparing to leave Frankfurt an der Oder, he advised Liddel to go to Wrocław and study with Paul Wittich.
- Liddel studied under Wittich at Wrocław for over a year before returning to Frankfurt an der Oder.
- In 1587 an epidemic broke out in Frankfurt an der Oder and Liddel left the town, moving to the University of Rostock.
- It may well be that Liddel went there at the suggestion of John Craig for, Johannes Caselius (1533-1613), the Professor of Rhetoric at Rostock, clearly knew Craig and wrote to him about Liddel.
- Mr Liddel was the first person in Germany, who explained the motions of the heavenly bodies, according to the three different hypotheses of Ptolemy, Copernicus, and Tycho Brahe.
- Liddel always claimed that he gave Brahe full credit for his system, but he clearly added his own mathematical details, which was probably the source of the confusion.
- It was Caselius who wrote a letter of recommendation for Liddel to the Academic Senate of Helmstadt, dated 1 January 1591, in which he stressed Liddel's mathematical expertise and his close connection to Brucaeus and his acquaintance with Brahe.
- On 24 July 1591 Liddel took up employment at the University of Helmstadt and spent many years teaching mathematics there.
- The magnificent auditorium, the Juleum Novum, opened in 1592 shortly after Liddel began teaching there.
- The Julian Academy had two chairs of mathematics, and soon after he came to Helmstadt, Liddel was appointed to the lower of the two chairs.
- After his death, Liddel was promoted to the higher chair of mathematics at Helmstadt in 1593 and Simon Mencius, already the professor of Latin, was appointed to the lower chair.
- In his first year of teaching in the higher chair Liddel gave the two courses (i) Geometriae fundamenta figurarum usum et geodesiam una cum triangulorum doctrina Ⓣ(Foundations of geodesic geometry with triangles) and (ii) Theoriae coelestium motuum iuxta triplicem hypothesin una cum tabularum tum Alphonsinarum quam Prutenicarum explicatione Ⓣ(Theory of celestial motion and explanations of the Alphonsine and Prutenic tables).
- Liddel stayed in Helmstedt until 1607, when he returned to Aberdeen with his mathematical books, among which were two copies of 'De revolutionibus'Ⓣ(On the revolutions (of the heavenly spheres)) and a rare handwritten copy of Copernicus's 'Commentariolus' Ⓣ(Commentaries).
- Back in Scotland, Liddel lived on his estate at Pitmedden, within a few kilometres of Aberdeen.

Born 1561, Aberdeen, Scotland. Died 17 December 1613, Aberdeen, Scotland.

View full biography at MacTutor

Origin Scotland

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive