PERMANENCE OF CONTINENTS AND OCEANIC BASINS. 135 



north o£ Cape Hatteras, and in the Gulf of Mexico, the con- 

 tinental line of one hundred fathoms is most plainly marked, 

 forming the upper edge of the more or less abrupt descent lead- 

 ing into deep water with a regular inclination. Owing to the 

 absence of this hundred-fathom line south of Cape Hatteras, it 

 became an interesting problem to trace the exact profile of that 

 part of the coast, and to continue it into deep water. The sea- 

 son of 1881 was spent by Commander Bartlett in the " Blake," 

 under the direction of the Hon. Carlile P. Patterson, the late 

 Superintendent of the Coast Survey, in running a number of 

 lines normal to the coast, south of Cape Hatteras and north of 

 the Bahamas, and carrying them into deep water. The Super- 

 intendent of the Coast Survey has kindly allowed me to make 

 use of the results of Commander Bartlett in connection with 

 my report of the dredging expeditions of the " Blake." ^ 



As was to a certain extent anticipated, the lines developed an 

 immense plateau, of a triangular shape, reaching from the Ba- 

 hamas to a point immediately south of Cape Hatteras, where this 

 plateau passes into the northern continental shelf, limited by 

 the hundred-fathom line. 



The eastern edge of this plateau is from three hundred to 

 three hundred and fifty miles from the coast, and w^th an ab- 

 rupt slope passes into deep water. For the sake of brevity I 

 shaU call it the " Blake Plateau." (See Figs. 56, 176.) The 

 eastern edge of the slope of the Blake Plateau commences at an 

 average depth of at least four hundred fathoms, so that the 

 general profile of the lines carried normally across it shows a 

 gradual incline from the shore to a depth of about fifty fath- 

 oms, then a somewhat abrupt slope to a depth of about four 



^ These liues have, during the season ant-Commander Brownson proved further 



of 1882-83, been extended south of the that to the south the eastern edge of the 



Bahamas as far as Porto Rico. Under Bahama Bank ran but a short distance 



the direction of Professor Hilgard, the seaward parallel to the general line of the 



" Blake," in command of Lieutenant- outer row of islands of the group, till it 



Commander Brownson, U. S. N., ran nor- united with the plateau upon which Porto 



mals into deep water, showing that the Rico and the Caribbean Islands crop out, 



Blake Plateau developed by Commander leaving probably one or two deep pas- 



Bartlett commences slightly to the west- sages extending towards the old Bahama 



ward of Great Abaco, and extends thence Channel north of San Domingo and Cuba, 



northward. (See Figs. 56, 176.) Lieuten- leading to the Windward Passage. 



