These are copies of material, mainly letters, not filmed for the Archive for the History of Quantum Physics (see PAAV86-A21). There is an interesting letter from Charle G. Darwin (1932) referring to Paul Ehrenfest, letters about the state of physics at Northwestern University from R. A. Fisher and B. J. Spence, and a letter by Hermann Weyl outlining a talk he was to give in Boston in December 1928.

Primary source materials for the history of quantum physics in the twentieth century, collected under the auspices of the American Philosophical Society and the American Physical Society, with a grant from the National Science Foundation.