Correspondence with individuals who temporarily held positions as observers or visited the Royal Observatory and used its instruments, 1880-1919. The correspondents are F.F. Adams, B. Balland, B.F. Bawtree, A.J. Coleman, Lt. Cust, B. Douglas, Ann Field, F.C. Hanning Lee, Captain Haynes, Lt. Henning, S. Hirayame, E.P. Hubble, N. Liapine, W.J. Luyten, Lt. Monro, K. Popoff, C.F. Richardson, M. Royds, W. Shaw, W.S. Smart, Lt. M.H. Smythe, G. Straham, W.H. Wagstaff, A. Wise and H. Young.