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The first method of exploring the ocean floor and mapping its sediments was the use of tallowed lead weights at the end of sounding lines. Seamen often cast the lead on approaching land during fog, and when they encountered a large area of shallow mud bottom, known as the “Block Island soundings,” between Martha’s Vineyard and Long Island, they knew their position along the coast (Pour-tales, 1871, 1872). The general characteristics of many samples taken with lead line by ships belonging to the Coast and Geodetic Survey were described by Pourtales (1871, 1872), and their content of foraminifers was reported by Pourtales (1850) and Bailey (1851, 1854). On the basis of 9,000 such samples, Pourtales (1870) compiled the first general bottom-sediment chart of the continental shelf for the area between Cape Cod and Key West. Notations of the character of the bottom also were written on field sheets and published navigational charts, and they were used by Shepard (1932) in a general study of the distribution patterns on continental shelves, particularly those of the Atlantic coast of the United States. During World War II these notations also were used for making large-scale bottom-sediment charts to help estimate the probable ranges for acoustic detection between submarines and surface ships. Charts were made by the United States Navy under the direction of H. C. Stetson and also by the German Navy (Oberkommando der Kreigsmarine, 1943).

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