Walter Carl Ferdinand Zabel, born 1892 in Bromberg/Posen, studied from summer 1911 to summer 1912 in Breslau and from winter 1912 to summer 1914 in Göttingen. From 1914 to 1919 he joined the military service, but must have had time to hear a lecture of Einstein in the winter 1917/18 at the university of Berlin without being registered. From 1919 to 1920 he finished his studies in Halle and worked afterwards until his retirement in 1957 as a teacher at a gymnasium in Berlin-Tempelhof. He died in 1968 leaving behind two carefully written volumes with lecture notes.
The first volume contains essentially a comprehensive lecture of David Hilbert on the foundations of mathematics. As an appendix to this lecture, Zabel copied a publication of Minkowski's famous 1908 lecture on space and time. The second volume begins with another lecture of Hilbert, a lecture on analytical mechanics at the university of Göttingen in winter 1913/14. The volume continues after the interruption of Zabel's studies with a lecture of Grammel on hydrodynamics at the university of Halle in summer 1919. The volumes ends with notes taken at Einstein's lecture on statistical mechanics at the university of Berlin in Winter 1917/18. In contrast to other lecture notes, these notes are written on bad quality paper and incompletely worked out, obviously as a consequence of the war. Zabel kept, however, stenographic notes of the parts missing at the end.