done on the Continental Slope and in the adjacent 

 ocean basins, largely as a result of (1) an increased 

 interest in the life of abyssal regions, (2) increas- 

 ing activity in the laying of submarine telegraph 

 cables, and (3) the development of deep sea wire- 

 sounding machines (Agassiz, 1888; Tanner, 1897). 

 From 1877 to 1880 Alexander Agassiz (1888) di- 

 rected surveys aboard the Coast Survey ship Blake 

 along the Atlantic Continental Slope, but it was 

 not until 1882 that the shelf itself was again sur- 

 veyed, this time from Montauk Point, Long Island, 

 to Cape Henlopen, Del. (no. 1558, scale 1 : 300,- 

 000). This survey was extended south to Cape 

 Charles in 1886 (no. 1720, scale 1:200,000) and 

 to the east as far as Georges Bank during 1887- 

 1889 (nos. 1782, scale 1:300,000; and 1837, scale 

 1:400,000). In all of these early surveys, the 

 soundings were by lead line and the navigation 

 was by shore sightings, astronomical fixes, and 

 dead reckoning. 



Except for a few isolated investigations of shoal 

 areas, the Middle Atlantic Shelf was not again 

 systematically surveyed until the 1930's, when 

 new sounding and navigational methods had been 

 developed. These surveys, from Georges Bank to 

 Cape Henry and from the shore to the Continental 

 Slope and Rise, are the principal sources used for 

 constructing the maps discussed in this paper. 



Several earlier bathymetric maps -were based on 

 the surveys of the 1930's. Tlie first and most fa- 

 mous are the maps of Veatch and Smith (1939) — 

 see also Smith (1939). These authors compiled a 

 series of charts of the Continental Slope fi'om 

 Georges Bank to Chesapeake Bay and of the Hud- 

 son Channel region of the shelf (scale 1 : 120,000) . 

 Uchupi (1965), in cooperative work by the Woods 

 Hole Oceanographic Institution and the U.S. 

 Geological Survey, used the sui'veys to compile a 

 1 : 1,000,000 scale map of the shelf, slope, and rise 

 from southern Canada to the Straits of Florida. 

 In addition, the USCGS has used tlie surveys to 

 construct nautical charts of the region at scales 

 of 1 : 80,000 and 1 : 400,000 (see the 1100 and 1200 

 series of nautical charts). The surveys have also 

 been used for small maps, published as text illus- 

 trations (e.g., Elliott, Myers, and Tressler, 1955; 

 Garrison and McMaster, 1966) . 



Present Data Sources 



The data from 39 USCGS hydrographic sur- 

 veys, made between 1932 and 1961, were used for 



making the present maps. (The smooth sheets of 

 these surveys vary in scale from 1 : 20,000 to 

 1 : 120,000.) In addition, 25 published USCGS nau- 

 tical charts (scales 1:10,000 to 1:80,000) were 

 used for some nearsliore areas, bays, sounds, and 

 harbors. The land contours which appear on some 

 sheets were compiled from U.S. Geological Sur- 

 vey and Army Map Service topographic quad- 

 rangle maps (scales 1 : 24,000 and 1 : 62,500). The 

 Long Island contours are from a topographic map 

 of the Island, scale 1 : 125,000, appearing in Fuller 

 (1914). 



More bathymetric information exists than was 

 used in the present compilation. Many miles of 

 sounding lines have been run on the Middle Atlan- 

 tic Continental Shelf by the research ships of 

 \'arious government agencies, private research in- 

 stitutions, and universities. Many of these data ai-e 

 equal in quality to those used, but most have not 

 been reduced and plotted in a form that can be 

 readily contoured. 



The new developments in the surveys of the 

 1930's were ecliosounding and radio-acoustic rang- 

 ing. Echosounding was developed in both the 

 United States and Europe during the first part 

 of this century, and by 1923 the USCGS had in- 

 stalled their first echosounder. This method of 

 measuring depths was rapidly improved and soon 

 rejolaced tlie older lead line and wire-sounding 

 machine. Before the 1930's, positions were deter- 

 mined in much the same manner as they were in 

 1842 and before. During the early 1920's, offshore 

 positioning had developed into an elaborate system 

 of precise dead reckoning, but it was not until the 

 USCGS introduced radio-acoustic ranging in 1924 

 that methods of navigation were changed funda- 

 mentally (Adams, 1942). This new method was 

 continually improved througliout ihe surveys of 

 the 1930's and was replaced by wholly electronic 

 systems during the 1940's. 



Methods of Construction 



Bathymetric contour lines were drawn directly 

 on either (1) full-scale, corrected copies of the 

 original surveys (smooth sheets), or (2) on nauti- 

 cal charts of nearshore areas. Louis E. Garrison 

 contoured the area between about long. 69°25' and 

 72°00' W. and shallower than about 100 fm. (US 

 CGS Hydrographic Surveys 6331, 6347, 6440, 

 6441, and 6447). I contoured the rest of the area. 



This contoured source material was transferred 



40 



U.S. FISH AND WILDLIFE SEEVICE 



