TOPOGRAPHY OF THE EASTERN COAST. 97 



son found nineteen hundred and seventy-six fathoms only two 

 and a half miles from land, — a declivity of thirty-eight degrees. 

 The thousand, two -thousand, and twenty-five-hundred fathom 

 lines run parallel to the general line of the eastern row of 

 islands which form the Bahama Bank, from Navidad Bank to 

 Great Abaeo Island. Between Navidad Bank and San Do- 

 mingo, a deep and narrow tongue of the ocean, averaging over 

 two thousand fathoms in depth, extends to opposite the centre 

 of the Windward Passage. The same steep slope is continued 

 north of San Domingo, Porto Rico, the Virgiu Islands, along the 

 eastern edge of the Windward Islands, till about off St. Lucia, 

 where the slope is somewhat less abrupt. The thousand-fathom 

 line follows closely the trend of the Windward Islands ; but the 

 two-thousand-fathom line begins to diverge off Anguilla and St. 

 Barthelemy, and by running at a considerable distance outside 

 of the Barbados forms a gentler slope than to the north. From 

 off the Caicos Islands the slope is still steeper, a depth of nearly 

 three thousand fathoms being found from there to the Virgin 

 Islands, at a distance of generally less than fifty miles, and often 

 within twenty miles of the hundred-fathom line. The greatest 

 depth reached by the " Blake " has been found off Porto Rico. 

 Lieutenant-Commander Brownson sounded there in four thou- 

 sand five hundi-ed and sixty-one fathoms,^ the deepest sounding 

 but one yet made, and traced the extension of the deep water 

 which fills the basin of the Western Atlantic to the west of the 

 Bermudas, and is separated from the deep basin of the tropical 

 Atlantic by a spur of the Dolphin Rise, to the north of St. Paul's 

 Rocks. The temperature, thirty -six and a quarter degrees, 

 clearly indicates that this deep hole, as well as the body of cold 

 water of which it is a part, is also separated by a ridge, which 

 probably rises to a depth of about seventeen hundred fathoms, 

 from the colder water of the South Atlantic ; there the tem- 

 perature is less than freezing, and the water is directly con- 

 nected with the Antarctic on the eastern part of the South 

 Atlantic. (See Fig. 61.) 



* Fifteen miles from the deepest point with brown ooze on the top and an onder- 

 the " Blake " sounded, in four thousand stratum of gray ; temperature, 36° F. 

 two hundred and twenty-three fathoms. 



