**Joost Bürgi** He was born on February 28, 1522 in Lichtensteig, Switzerland, and died on January 31, 1632 in Kassel (now Germany). He was the most skillful, and most famous man who worked with watches in his day. He also made important scientific instruments, notably for Hesse-Kassel Wilhelm der Weise's Landgraf, who combined governing his state with being a first-class astronomer. (Although historians do not usually mention this fact, Landgraf's observations, particularly those of fixed stars, were generally at least as accurate as Tycho Brahe.)

**D**thereafter Bürgi also worked for the Roman Emperor Rudolph II, and his successor Matthias (in Prague). Bürgi became interested in mathematics, and it was to him that Johannes Kepler (1571-1630), the then Imperial Mathematician, was indebted for his introduction to Algebra. In return, it seems to have been Kepler who persuaded Bürgi to write his original and interesting work on logarithms (the manuscript is largely in Kepler's handwriting), printed in 1620. Bürgi's method is different from Napier's method and was clearly independently invented.

Bibliography: Article by: J. V. Field, London, August 1995.