Old maps, made before the American Revolution, show a large bank off the New England coast, extending from Nantucket Shoals to southern Nova Scotia. This bank was formerly called Saint Georges Bank but is now known as Georges Bank. This shoal-water fishing ground has proved to be less extensive than it was formerly considered to be (Fig. 1). It is distinctly bounded about 100 miles south of the Nova Scotia peninsula by a deep channel, which will be referred to as Northeast Trough. This trough extends out between Browns Bank and Georges Bank, connecting inside with the deep portions of the Gulf of Maine. Farther northeast along the continental shelf a series of discontinuous banks culminates in the Grand Banks of Newfoundland.
All these shoal areas have certain features in common. They are found, for the most part, at or near the outer margins of the shelf. Their surfaces are . . .