NORTH ATLANTIC SOUNDINGS: The study of the North Atlantic deep-sea bathymetry began a little more than a century ago with the taking of the first deep-sea soundings by lead line. By 1860, largely because of the great public interest in the proposed trans-Atlantic cables and the enthusiastic encouragement of Matthew F. Maury (1855), several hundred soundings had been taken in the North Atlantic in depths greater than 1000 fathoms. Meanwhile, on either side of the Atlantic surveys of coasts, harbors, offshore banks, and the continental shelf were being made for navigational use. The Hudson Submarine Channel and the head of the Hudson Canyon were discovered by the United States Coast Survey during this period. By 1912 more than 1800 deep-sea soundings had been taken in the North Atlantic by the laborious method of using a lead lowered at first by hemp line and later by wire. Between 1900 and 1920 Fessenden in the United States, Behm in Germany, and Langevin and Florisson in France established that acoustic echo sounding was possible and built machines to take echo soundings. In 1922, echo sounding became a practical operation. Although many of the early echo sounders were fitted with automatic recorders, they were in general suitable only for use in shallow water (less than 500 fathoms). Deep-sea echo soundings were obtained by listening on earphones for the returning echo and timing the interval by eye with a suitable clock. The improvement of sounding gear continued, and by the mid 1930's automatic recording deep-sea echo sounders were manufactured and put into limited use, although, by and large, all pre-World War II deep-sea (> 1000 fathoms) echo soundings were discrete observations by the "ear and eye" method. A good review of pre-World War II echo-sounding apparatus is given in a publication of the International Hydrographic Bureau (Anon., 1939). During the war the NMC[1] echo sounder was developed and installed on many U. S. ships. It was adequate for deep-sea sounding if in perfect condition; but the designers, being cautious, had arranged for recording only in the depth range of 0-2000 fathoms. The NMC sounder on Atlantis was modified to record in greater depths in 1945, and many thousands of miles of tracks were obtained of the deep sea with this apparatus. The NMC had a small record chart (6¼ inches = 2000 fathoms; ½ inch = about 3 miles). The precision was low since the apparatus depended on a ship's regular AC power supply for its time standard. A new sounder, the UQN-1B, was developed in the United States following World War II. The instrument as manufactured recorded on an extremely small chart (8 inches = 6000 fathoms) but could be modified for multiple 600-fathom scale recording (8 inches = 600 fathoms). The timing function was usually accomplished by poorly regulated ship's AC power supply, and errors were consequently large (Dietz, 1954; Heezen, 1954). In addition, the stylus arrangement required constant adjustment.