CONSTRUCTION OF THE MAPS 



Construction of the maps is discussed from 

 three aspects: (1) history of past surveys, (2) 

 study of present surve3's, and (3) methods of 

 construction. 



Past Bathymetric Surveys 



The first systematic bathymetric survey of the 

 entire width of tlie Middle Atlantic Continental 

 Shelf was made by the U.S. Coast Survey in 1842 

 (USCGS Hydrographic Survey no. 100, scale 

 1 : 400,000) . Previously, only some inshore ai-eas 



had been systematically surveyed, and charts of 

 the offshore regions were based on a few isolated 

 soundings. The 1842 survey covered the area be- 

 tween Rhode Island Sound and Cape May and 

 from near shore to a little over 100 fm. It was 

 supplemented in 1844 by a survey covering much 

 the same area (no. 101, scale 1 ; 400,000) and again 

 in 1859 by a survey extending fi-om Mart.ha's 

 Vineyard to sliglitly south of Cape Henlopen, 

 Del. ( no. 670, scale 1 : 400,000) . 



No surveys were made during the Civil War, 

 but in the 1870's and 1880's much sounding was 



BATHYMETRIC MAPS AND GEOMOEPHOLOGY OF MIDDLE ATLANTIC CONTINENTAL SHELF 



39 



