64 A tidal delta in Shark River Inlet, Belmar, N. J. (v) 82 65 A tidal delta, Popes Creek on the lower Potomac River, Virginia (o) 83 66 A double tidal delta at Barnegat Inlet, New Jersey (v) 84 67 A tidal inlet through the barrier beach south of Beach Haven, N. J. (v) 85 68 Beach between Brigantine and Little Egg Inlets, New Jersey (v) 86 69 A simple spit: Lower Cedar Point, Maryland, on the lower Potomac River (o) 87 70 A recurved spit south of Brigantine Inlet, New Jersey (v) 88 71 A recurved spit showing interference with natural growth: The northern end of Ocean City, N. J. (v) 89 72 New Point Comfort at the tip of the York-Rappahannock peninsula, Virginia (v) 90 73 Spit at Tucker Beach, New Jersey (v) 91 74 A land-tied island: Napatree Point, near Watch Hill, R. I. (v) 92 75 Powells Creek, Virginia, on the lower Potomac River (o) 93 76 Roberts Creek, a drowned river valley southeast of Yorktown, Va. (v) 94 77 The underwater channel in Quantico Bay on the lower Potomac River, Virginia (v) 95 78 Natural channels and shoals near Miami. Fla. (o) 96 79 A dredged channel at Miami, Fla. (o) 97 80 A shoal in Hereford Inlet north of Wildwood, N. J. (v) 98 81 Sand bars at Cape Charles, Va. (v) 99 82 Bars, channels, beaches, and marsh near Far Rockaway, Long Island, N. Y. (v) 100 _All of the airplane photographs in this book, both oblique and vertical, were taken by the United States Army Air Service, except Figs. 78 and 79, which were taken by the United States Navy Air Service, and Figs. 10, 65, 69, 75, 77, and 82, which were taken by the author. To these two services the author is indebted for the permission to reproduce their photographs, and this acknowledgment is made with the same force as if made individually under each illustration._ _As a guide to the evaluation of the scale of the vertical photographs, which is expressed under each photograph in the form of the natural scale, or representative fraction, the following approximate equivalents may be borne in mind_: _1:10,000 = 800+ feet to the inch_ _1:16,000 = ¼ mile to the inch_ _1:21,000 = ⅓ mile to the inch_ INTRODUCTION