Christoph Jetzler und Leonhard Euler

Abstract

Christoph Jetzler (1734–1791), a Swiss furrier and amateur mathematician from Schaffhausen, came to Berlin in spring 1763, only to ask a favour of Leonhard Euler, whom he had never met before. He wanted to copy the manuscript of Euler’s Institutiones Calculi Integralis (integral calculus), which had not appeared in print yet. The request was granted, and a copy of about 1000 pages was completed in the autumn of the same year.

As his letter of March 4th 1765 (the only one extant) shows, Euler kept in touch with Jetzler. The letter deals with the integration of a special ordinary differential equation and with singular solutions of certain differential equations. It is a showpiece of Euler’s didactical abilities and will be published here in full with some introductory passages from Jetzler’s biography (written by Rudolf Wolf in 1859).