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 Abaco 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 Virgin 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 hundred 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.) 
1 Fifteen miles from the deepest point with brown ooze on the top and an under- 
the “Blake” sounded, in four thousand stratum of gray ; temperature, 36° F. 
two hundred and twenty-three fathoms, 
