Sweet Hall Marsh, Virginia, 34 (ill.), 35 (map), 39 Swiss school of hill shading, 66 Terraces, underwater, 15, 94 (ill.) Texas-Oklahoma boundary, 51 (ill.) Thomas, H. H., 101 Thoroughfares, 34 (ill.), 35 (map), 39; Eltham Marsh, 36 (ill.) Tidal Basin, Washington, D. C., 16 (ill.) Tidal deltas, 82 (ill.), 83 (ill.); Barnegat Inlet, 84 (ill.), 85 Tidal inlet, Beach Haven, N. J., 85 (ill.) Tidal marshes, stream development, 28 (ill.) Tied island, 77 (ill.); development--Napatree Point, Rhode Island, 92 (ill.) Tombolos, 92 (ill.) Topographic mapping, 72 Treasury Building, Washington, D. C., 16 (ill.) Trees, 13 (ill.) Tucker Beach, New Jersey, spit, 91 (ill.) Underwater topography, 45; best conditions for photographing, 47; channel in Quantico Bay, 95 (ill.); channels (natural) at Miami, Fla., 96 (ill.), 102; channels, shoals, terraces--Roberts Creek, Virginia, 94 (ill.); Chesapeake Bay, 90 (ill.) United States Army Air Service, viii, xi, xii United States Coast and Geodetic Survey, 74; coast line charting, 87, 88; Florida coast experiment, 93 United States Geological Survey, co-operation, xii United States Land Office, 56 United States Military Academy, 8 (ill.) United States Naval Academy, 7, 9 (ill.) United States Naval Observatory, 13 (ill.) United States Navy Air Service, viii, xi, xii Vertical photographs, 1; scale, viii, 74; horizontal control, 74 Viewpoint, 1 Village, prototype, 54 (ill.) Virginia, Eastern Shore mud-flat area, stream system, 41, 42 (ill.), 43 (ill.); tidewater portion, 38 Visibility under water, 102 Volcanic craters. _See_ Craters Volmat, J., 99, 101 War and Navy offices, new, Washington, D. C., 16 (ill.) Wards Island, 15 (ill.) Warwick Creek and Mulberry Island, Virginia, 24 (ill.), 25 (map) Washington, D. C., Capitol, frontispiece, 7; Library of Congress, 7; mapping, 79; part showing White House, Treasury, and many familiar features, 16 (ill.); topographic map, part, opp. 22; United States Naval Observatory, 13 (ill.) Washington Column, California, 60 (ill.) Washington Monument, 16 (ill.) Wash-overs, 81 (ill.), 86 (ill.) Watch Hill, R. I., 92 Water, Visibility under, 102 West Point, N. Y., United States Military Academy at, 2, 8 (ill.) West Point, Va., 36 (ill.), 38; marshes, 29, 30 (ill.) White House, Washington, D. C., 16 (ill.) Wichita Falls, Tex., 51 Wildwood, N. J., 98 Wintun Glacier, 58 (ill.) Wright, Orville, ix Wright, Wilbur, ix York River, 38, 76, 83, 87; shoreline, 77 (ill.) Yosemite and Mt. Lyell topographic sheets, 61 Yosemite Valley, 60 (ill.), 61 (map) FOOTNOTES: [1] Cf. his The Use of the Panoramic Camera in Topographic Surveying, With Notes on the Application of Photogrammetry to Aerial Surveys, _U. S. Geol. Surrey Bull. 657_, Washington, D. C., 1917. [2] H. E. Ives: Airplane Photography, Philadelphia, 1920, pp. 328-350.