BIOGRAPHIES 379 1904-1908, technical expert at Swiss Patent Office, hired on Einstein's recom- mendation. 1908-1909, winter semester, audited Einstein's course on theory of radiation at University of Bern. 1909-1910, worked as consulting engineer and pursued self-study in Bern. 1910-1915, worked for textile and insurance firms in Gorizia, Italy. 1915, returned to Switzerland. 1916-1918, lived in Zurich acted as intermediary between Einstein and Maric during their separation helped care for their sons during Maric's illness. 1916, appointed Privatdozent in patent law at ETH. 1918-1919, catalogued his uncle's library in Rome. 1920-1938, worked at Swiss Patent Office in Bern and taught patent law once a week at ETH in Zurich. 1926, Einstein intervened on his behalf when an attempt was made to dismiss him from Patent Office. 1930, met with Einstein for the last time. 1939-1944, lived in Geneva after retiring. 1944-1945, lived with son in Petit-Saconnex after wife's death lectured to war refugees in work camps. Einstein thanked him for "manche wertvolle Anregung" in his 1905 paper on special relativity Einstein characterized him as a perpetual student. Sources: Einstein/Besso 1972 and Einstein correspondence with Maric. Ehrat, Jakob b. 27 January 1876 in Schaffhausen d. 18 March 1960 in Uerikon, canton of Zurich ETH classmate, friend, and correspondent of Einstein. Son of a baker. At- tended Gymnasium in Schaffhausen. 1896-1897, first semester, studied at University of Zurich second semester, studied at ETH, faculty of engineer- ing. 1897-1900, studied mathematics at ETH, Section VI A, where he met Einstein. 1900-1903, Assistent to ETH mathematics professors F. Rudio, A. Hurwitz, and J. J. Rebstein. 1904-1908, instructor at boarding school in Bieberstein/Rhön, Bavaria. 1906, University of Zurich doctoral dissertation. "Uber das Algebraischwerden der Integrale irrationaler Differentiale ...," supervised by C. F. Geiser. 1908-1911, Assistent to Marcel Grossmann at ETH teaching aide at Kantonsschule, Zurich. 1910-1945, teacher of mathe- matics and accounting at Gymnasium, Winterthur. 1914, married Margrit Schmid, with whom he had two children. 1926, underwent operation for detached retina. 1945-1960, lived in Richterswil and Uerikon after retiring. Sources: Hans Ulrich Wipf, "Jakob Ehrat und Albert Einstein. Skizze einer Freundschaft," Schaffhauser Mappe (1973), pp. 29-30 curricu- lum vitae, SzZSa, records of Kantonsschule, Zurich correspondence with Einstein.