the theoretical physics then being developed. The Courant-Hilbert book fortuitously contained the mathematics necessary for the development of the Heisenberg-Born matrix mechanics formulation of quantum mechanics and also for Schrödinger’s wave mechanics formulation, both put forward in 1925. The main thrust of Ewald’s work was X-ray crystallography, and Ewald was the eponym of Ewald construction and the Ewald sphere, both useful constructs in that field. In 1929, in order to remove confusion from the proliferation of crystallographic data, Ewald proposed review and collection of the best data into a single publication. The results were published in 1935 as the Internationale Tabellen zur Bestimmung von Kristallstrukturen. Another contribution by Ewald, published in 1931, Strukturbericht Volume I (1913-1928) was edited by Ewald and C. Hermann. Ewald was elected Rector at Stuttgart in 1932. However, due to increasing difficulties with faculty who were members of National Socialism in Germany, he resigned his position in the spring of 1933, one year before his term was due to expire. Ewald continued with his other activities. However, over increasing problems with the Dozentenbund, Wilhelm Stortz, University Rector, asked Ewald to leave. He emigrated to England in 1937 along with his mother, the painter Clara Ewald, and took a research position in Cambridge, until he was offered and accepted a lectureship at Queen's University Belfast in 1939. He later became a professor of mathematical physics. While lecturing at Duke University in 1937, Hans Bethe, who got his doctorate under Sommerfeld in 1928, bumped into Ewald's daughter Rose, who had already emigrated to the United States and who was attending the school. They were married in September 1939. Thus, Bethe became son-in-law to Paul Peter Ewald. Near the end of World War II, Sommerfeld organized his lecture notes and began writing the six-volume Lectures on Theoretical Physics. While at the Polytechnic Institute of Brooklyn, Ewald wrote a Foreword to Sommerfeld’s Course, which appeared in the English translation of Sommerfeld’s work. Also, toward the end of World War II, Ewald was concerned that peace would result in the establishment of multiple, competing national journals of crystallography. So, in 1944, at Oxford, he proposed the establishment of an International Union of Crystallography (IUCr) that would have sole responsibility for publishing crystallographic research. In 1946, he was elected Chairman of the Provisional International Crystallographic Committee, in a London meeting of crystallographers, from 13 countries; he served in this capacity until 1948,