{Dorothy N. Davis; Dartmouth College, Baker Memorial Library; L. P. Delsasso; Denver Public Library; Debrecen University Physical Institute; Rev. C. E. Deppermann, S.J.; Detroit Public Library; Deutsche Physikalische Gesellschaft; Deutsches Museum; L. E. Dickson}
{California State Library; José da Silveira Camerino; Francis A. Campbell; Léon Cap; R. Stanley Capon; Ellsworth Carpenter; F. E. Carr; Carter Observatory [R. C. Hayes]; S. Chapman; Rev. Stanislaus Chevalier, S.J.; Christian Science Monitor [Robert K. Shellaby]; Christiania University Observatory}
{Clara Robinson; Ruth Stone [Mrs. C. C.] Robinson; Rev. Luis Rodés, S.J.; Guy Rose; H. Rosenberg; Royal Institution, London; Royal Society of Edinburgh; Royal Society of London; Walter Russell; Ryerson Physical Laboratory; P. M. Ryves}
{Aug. Collard; T. Collodi; F. Barrows Colton; Commission for Russian Scientists; A. Pribar de Conill; Duvall Cooper; Copernicus 450th Anniversary; Corning Glass Works; A. L. Cortie, S.J.; Robert Coughran; G. Cramer Dry Plate Co.; R. T. Crawford; Henry Crew; Raymond E. Crowtherb [Kodak, London]; James Cuffey}
{Herbert Dingle [lecture & notes by FHS on "Science and the Unobservable"]; Harold B. Dirks; Roberta Lloyd [Mrs. Hugh T.] Dobbins [re S. Pike's grave]; Dorpat University Meteorological Observatory; E. Doublet; John C. Duncan; R. S. Dugan; Theodore Dunham, Jr.; Theodore Dufur; O. L. Dustheimer}
{Fr. R. Cirera, S.J.; Cpt. P. Civalleri, R.I.N.; Civic Bureau of Music and Art of Los Angeles; Claremont Colleges; Nell Ray Clarke; --Clasen; Gerald Coffman}
{Albert Chase McArthur; Macbeth Daylighting Co., Inc. [Norman Macbeth]; Lucena McBride; Phoebe Merl McClees [ltrs M. E. Churchill ?? FHS; FHS ? Fisk Teachers' Agencies]; Frank McCoy; E. C. MacDowell; Anita Newcomb McGee; McGill University; Dean B. McLaughlin; MacMillan Co. Publishers [Rose Levy]; Mrs. John McMillan; Maud W. Makemson; E. Mallinckrodt, Jr.; Marburg University Library; Marchaut Calculating Machine Co. [folded]; W. L. Marcy; Marina, Instituto y Observatorio de; Marquis, A. N. & Co.}
