them in Struve's stead; students were given some plate to measure and analyze in his absence.⁵⁶ Still, when it came to Ph.D. qualifying exams, Struve had a great interest in a high level of achievement. W. H. McCrea recalls that he was astonished to see how exacting Struve's standards were. He would not "lower the hurdle" but would give the student "the fullest possible opportunity to surmount it."⁵⁷ We can characterize Struve's attitude toward his colleagues and students thus: "It was unforgivable in his eyes for anyone to fall short of full commitment."⁵²

In spite of Struve's successes in building McDonald and pushing astrophysics ahead, a case could be made that his greatest accomplishment was making the Yerkes Observatory staff the brain trust it was in the 1930s and 1940s. Elvey we have already mentioned. W. W. Morgan finished his Ph.D. under Struve in 1931⁵⁸ and recalls, "His [Struve's] influence was far and away the most important in my formative years as an astronomer. He had an intense enthusiasm that he translated to me, and was the sound basis on which I was able to build."⁵⁹ In the summer of 1936 Gerard Kuiper was hired, and also Bengt Str ömgren (later Yerkes director, 1950-57). In 1937 S. Chandrasekhar, the brilliant mathematical astrophysicist, was hired. Other notables who were staff members include Jesse Greenstein, W. A. Hiltner, and Gerhard Herzberg. There were many visitors, such as Swings, Jan Oort, M. G. J. Minnaert, H. C. van de Hulst, and Albrecht Unsöld.

Struve worried about appearances, rank, and position. During the Depression he was concerned about hiring foreign astronomers when many Americans were out of work. When the wife of his deputy George van Biesbroeck wrote a letter to Belgium which was excerpted in a popular astronomy magazine and noted how Yerkes was being run by "the two Europeans," Struve was particularly angry.⁶⁰ That