Certainly, the air photograph is only in its infancy--but an infancy full of promise. As a means of securing new and advantageous views of subjects of interest, it is not only entertaining but scientifically and commercially valuable. As an aid in mapping it can, even in its present stage of development, serve an important purpose by supplying accurate knowledge of otherwise inaccessible regions, by furnishing details that are valuable but expensive to obtain, and by permitting the frequent and inexpensive revision of existing maps. INDEX Accuracy, 1, 74 Acknowledgments, viii, xi Aerial photo-hydrography, 99 Aerial photo-topography, 93 Air photographs, how to read, 4; improvements under way, 102; oblique and vertical, 1; value in coast charting, 93, 99, 101 Air photography, application, ix; development, ix; elements to be recorded, 2; outlook, 102 Air Services, co-operation, xi Aircraft, x Airplane photography. _See_ Air photography Aliso Creek, California, 68 Amundsen, Roald, 71 Anacostia flats, D. C., 12 Anacostia River, 13, 22 (ill.); land along, mosaic photograph, opp. 32 (Fig. 13) Animal trails, 29, 39 Annapolis, 7. _See also_ United States Naval Academy Arabian coast, 101 Architects, 7, 11 Architecture, 11 Arizona, southern, 71 Arroyos, 61, 65 (ill.) Atlantic City, N. J., 32 (ill.) Atlantic Coastal Plain, 27; meandering streams, 50; salt marsh areas, 32 (ill.); submarine land forms, 45 Atlantic Ocean, waves and surf, 91 (ill.) Back River, Virginia, 76 Bagley, J. W., xii, 74 Baltimore and Annapolis Railroad bridge, 9 (ill.), 10 Barnegat Bay, 85 Barnegat Inlet, 84 (ill.), 85 Barrier beaches, 41; between Brigantine and Little Egg Inlets, New Jersey, 86 (ill.); cities and surroundings, 32 (ill.); inlet formation through, 81 (ill.); Long Branch, N. J., 18 (ill.); tidal inlet through, Beach Haven, N. J., 85 (ill.). _See also_ Beaches Beach Haven, N. J., cusps, 80 (ill.); inlet formation through barrier beach, 81 (ill.); tidal inlet, 85 (ill.) Beaches, bluff and beach on shore of York River, 77 (ill.); cusps near Beach Haven, 80 (ill.); Far Rockaway, Long Island, 100 (ill.); sandy, with cusps--Sandy Hook, 78 (ill.). _See also_ Barrier beaches Bear’s Cut, Florida coast, 96 (ill.) Belmar, N. J., tidal delta, 82 (ill.) Benning, Camp, opp. 26, opp. 50 Benning, D. C., 13, 22 (ill.) Benning Road, 13 Benning Road Bridge, opp. 22 (ill. and map) Bidwell, Lake, California, 62 (ill.), 63 (map) Bluffs, 83; beach and bluff on shore of York River, 77 (ill.) Board of Surveys and Maps, 72 Boundary disputes, 26; Texas-Oklahoma, 51 (ill.) Braided channels, 50, 51 (ill.) Brigantine Inlet, New Jersey, 86 (ill.), 87; recurved spit, 88 (ill.) Bridges, 11; Baltimore and Annapolis Railroad, 9 (ill.), 10; Benning Road, opp. 22 (ill. and map); Hell Gate, 11, 15 (ill.); Pennsylvania Avenue, opp. 22 (ill. and map) Bronx Borough, Port Morris section, 15 (ill.)