**Jost Bürgi** was a Swiss mathematician who discovered logarithms independently of the Scottish mathematician Napier.

- It is conjectured that Jost Bürgi decided to leave Lichtensteig, partly because of the religious divide and partly because of the lack of educational opportunities in the small town.
- It is clear from the skills that he acquired over the floowing few years, that Bürgi must have served an apprenticeship to a blacksmith, instrument maker and watchmaker but no knowledge exists of the towns in which he served his apprenticeship.
- The Swiss mathematician Konrad Dasypodius, who was the professor of mathematics at the University of Strasbourg, had designed the astronomical clock and is likely that Bürgi acquired his expertise in mathematics from Dasypodius or his pupils.
- Although Bürgi never learnt Latin (the language of science at this time), he was very knowledgeable in mathematics and astronomy with skills compatible with having been immersed in the scientific circle in Strasbourg, but certainly not as part of a university course.
- Certainly Wilhelm was aware that Bürgi was the most skilful instrument maker of his day for he employed him from 1579.
- On 25 July 1579 the Landgraf of Hesse-Kassel Wilhelm IV asked Bürgi to become a watchmaker to the court in Kassel, to develop scientific instruments, and assist in the observation of stars which would confirm the heliocentric model described by Copernicus.
- As part of his duties Bürgi made sextants, celestial globes and highly accurate clocks for use in this Observatory.
- The Landgraf wrote to Tycho Brahe on 14 April 1586 telling him about a highly accurate clock which Bürgi had built which, for the first time, had a minute hand, registered seconds and had an error of less than a minute in 24 hours.
- Bürgi's clock had an innovative cross-beat escapement with an independent system added to the traditional wheel-train to give a considerably more constant pressure to the escapement so leading to the greater accuracy.
- After Rothmann left the Kassel Observatory in 1590, Bürgi became official mathematician and astronomer to the Court.
- In 1591 Bürgi became naturalised in the city of Kassel.
- Bürgi went on to teach the boy mathematics and astronomy to such a high level that he became one of the leading scientists of his day.
- The year 1591 was significant for Bürgi in yet another way, for in that year he completed his astronomical clock which was based on Copernicus's heliocentric system, quite a bold move at a time when the Church was moving against anyone holding heliocentric views.
- One could reasonably ask how Bürgi, who knew no Latin, could have known the details of the Copernican system and here we can give a clear answer since Nicolaus Reimers worked at the Observatory in Kassel in 1586-87 and made a translation of Copernicus's De revolutionibus orbium coelestium from Latin to German for Bürgi to study.
- By the time Bürgi made his astronomical clock he was using his own version of logarithms, invented for his own use to aid him in his astronomical calculations.
- To use these formulas, Bürgi computed sine tables called the Canon Sinuum which were never published and now sadly appear to be lost.
- On 4 July Bürgi had an audience with Rudolph in Prague, delivering the globe.
- Also in 1592 Bürgi obtained a patent for his surveying instrument based on the method of triangulation.
- In 1596, and again in 1604, Bürgi again travelled to Prague.
- He was given a workshop at Hradcany, Prague Castle, with two assistants and also worked with Kepler who was indebted to Bürgi for his introduction to algebra.
- There is strong evidence that Kepler got the idea for his third law of planetary motion from thinking about logarithms, and it must have been through discussions with Bürgi that logarithms were a common topic at Hradcany.
- Kepler persuaded Bürgi to write up his original and interesting work on logarithms (the manuscript is largely in Kepler's handwriting), and it was printed in 1620.
- Bürgi's method is different from that of Napier and was clearly invented independently.
- During the years that Bürgi worked in Prague, he made several visits back to Kassel.

Born 28 February 1552, Lichtensteig, St Gallen, Switzerland. Died 31 January 1632, Kassel, Hesse-Kassel (now Germany).

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Architecture, Astronomy, Origin Switzerland

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