The tripartite structure of the delta has been well known since the publication of Gilbert’s delightful classic on Lake Bonneville (Gilbert, 1890, p. 68–70, figs. 14, 15). That structure pertains as well to many marine embankments built on so vast a scale that their character as deltas is not always recognized. On coasts where currents are not sufficiently powerful to destroy them as fast as they are formed, these embankments are to be found extending for hundreds of kilometers seaward from the mouths of the great rivers of the earth. From the river mouths they extend also inland for hundreds of kilometers as broad plains, braided by distributaries at their shoreward margin. These plains are easily recognized as deltas, the limiting top surface in every case of a great embankment, built into the sea by the river with sediments brought by it from remote parts . . .