(1) Correspondence regarding various American observatories, 1938-1959, including correspondence with the Yale University Observatory; P. van de Kamp, Sproul Observatory, Pennsylvania; Yerkes Observatory; Carnegie Institution of Washington; G.C. McVittie, Department of Astronomy, University of Minnesota; Astronomical Department, Berkeley University; The Observatory, University of Michigan; Georgetown College Observatory; Dr James G. Baker, Professor Harlow Shapley and Dr Bart J. Bok, Harvard College Observatory; Dr I.S. Bowen and Dr Walter S. Adams, Mount Wilson and Mount Palomar Observatories; United States Naval Observatory, Washington; Dr A.N. Vyssotsky, Leander McCormick Observatory, University of Virginia, Charlottesville; Lick Observatory; and Dr Lyman Spitzer Junior, Princeton University Observatory, New Jersey. There is also a report on non-seasonal changes in the rate of rotation of the Earth, sent by Sir H, Spencer Jones to Professor D. Brouwer of the Yale University Observatory, 1953.

(2) Correspondence with the Lick Observatory, 1939-1959, including Dr Albert E. Whitford, Dr G.H. Herbig, C.D. Shane, J.H. Moore and Dr W.H. Wright. There are letters concerning the Martin Kellogg Fellowship at the observatory, 1940.

(3) Correspondence regarding the McMath Hulbert Observatory, University of Michigan, 1938-1940, including material on the McGregor Building and 70-foot tower telescope.

(4) Correspondence regarding the Mount Palomar and Mount Wilson Observatories, 1956-1959, including correspondence with Dr O.C. Wilson and Dr I.S. Bowen.