{E. H. Tipton; F. M. Tisdel; Richard C. Tolman; Treasury Department [C. W. Pendleton]; Triangle Photo Service [M. R. Rikon]; Karl J. Trübner; W. A. Trumbull; R. H. Tucker; Turkmenistan Observatory; Spencer D. Turner; Tuttle, Morehouse, and Taylor, Co.}
{R. A. Millikan; Monroe Calculating Machine Co. [folded. incl Calculator Equipment Corp.]; Montevideo, Observatory of the University of [folded]; Monthly Weather Review; Joseph Monti; K. Moór [?]; Ernest C. Moore; Morava Construction Co.; D. W. Morehouse [incl ltr H. Shapley ? DWM]; D. P. Moreton; G. W. Morey; --Moriceau; T. H. Morgan; Sylvanus G. Morley; W. D. Morrison; Albert G. Mowbray [incl memo EPH ? FHS]; F. R. Moulton; Z. Müller; Carlos S. Mundt}
{C. Addison Willis; H. C. Willis; Carl Wilson; Herbert C. Wilson; H. W. Wilson Co.; Latimer J. Wilson; Olin C. Wilson; Ralph E. Wilson; Clyde Wolfe; Coral Wolfe; Harry O. Wood; R. W. Wood; R. v. d. R. Woolley; J. H. Worthington}
{C. Easton; J. M. Eder; Frank K. Edmondson; W. S. Eichelberger; Greta Ekelöf; Ferdinand Ellerman [ltrs re FE's death: George E. Johnson ? FHS; FHS ? GEJ]; C. T. Elvey; Pio Emanuelli; Encyclopaedia Britannica [W. L. Dalton]; S. Enebo; Wilhelm Engelman, Publisher; Eugene H. Eyster}
{Donald G. Marsh; Hannah Mary Marsh; Thomas Marshall, Jr. [folded]; Massachusetts Institute of Technology Library; Masson and Co.; T. M. Martin; T. Matukama; A. S. D. [Mrs. T. F.] Maunder; Thomas Frid Maunder; Oscar Maurer; R. Newton Mayall; Edward L. Mayberry; Carroll B. Merritt; W. F. Meyer; A. A. Michailovsky; G. R. Miczaika; Dayton C. Miller; Freeman D. Miller; H. L. Miller; John A. Miller; Mrs. John Miller}
{Herbert Meredith Reese; F. P. Reilly; M. dos Reis; W. Reiter; Remeis Observatory, Bamberg; Rennselaer Polytechnic Institute Library; Republic Productions, Inc. [John T. Bourke]; D. J. Rhederg; E. W. Rice; Hugh S. Rice; C. R. Richards; Harold Richards; L. J. Richardson; R. G. D. Richardson; K. M. Richey}
