Vol. 58.] PHYSICAL DEVELOPMENT OF BARBADOS, ETC. 300 
While Barbados has a length of little more than 20 miles, the 
soundings show that the submerged ridge extends for 110 miles, 
and is covered by from 3000 to 4500 feet of water. ‘his ridge 
is abruptly terminated towards the south by a channel, where 
soundings attain a depth of 7200 feet, while on the north the 
indentation in the submarine plateau reaches to 9600 feet. Just 
north of it, a fragment of the platean—the Madiana Banks—comes 
to within 300 feet of the surface of the sea. In a north-westerly 
direction, towards Martinique, the submarine plateau is somewhat 
more depressed (8000 feet or more). To the north of the summit 
of this Barbados-Martinique ridge its character has not been deter- 
mined, except that between the outlying Madiana Banks and 
Martinique there is a depth of 9246 feet. South of the ridge is 
a hole or a valley reaching to a depth of 8958 feet, at a point west 
of Barbados. Elsewhere the embayment in the drowned plateau is 
not known to reach more than 7200 feet below sea-level. The 
amount of the depression here noted is in accord with that of the 
more confined valley-like indentations upon the western side of 
St. Lucia, St. Vincent, and the Grenadines. See the map (Pl. X) 
which accompanies the foregoing paper on Dominica, etc. 
Seaward of the Scotland Valley, the incomplete soundings on the 
edge of the narrow shelf show the usual evidence of two or three 
amphitheatres or cirques indenting the submarine plateau. 
Ill. Hyproerapuicat RELATIONSHIPS oF TRINIDAD. 
These are continental, with a channel between the island and 
the mainland of only 36 feet in depth. The Gulf of Paria is 
nowhere more than 96 feet deep, except at its mouth, where there is 
a valley revealed to a depth of 924 feet, or more than 600 feet 
beneath the adjacent floor of the submerged coastal plain, which 
extends nearly 50 miles farther seaward. The greatest submergence 
of the summit of the ridge between Trinidad and the Grenadines 
appears to be only 750 feet, although there may be an adjacent 
narrow channel of greater depth, as here the soundings are few in 
number. From this point the drowned plains gradually descend 
westward, and on the line between the nearest point of Trinidad 
and the Grenada banks the depth reaches to 2286 feet; but 
this line is indented by several cirques. Tobago rests upon the 
north-easterly extension of the continental shelf (which supports 
Trinidad), here submerged to about 200 feet, though indented on 
its north-western side by a cirque, with a depth of 408 feet. A 
more deeply-submerged spur extends north-eastward from Tobago 
towards the Barbados ridge, thus enclosing the large valley in the 
submarine Antillean plateau, with the Grenadines, St. Vincent, 
St. Lucia, Martinique and the ridge therefrom to Barbados almost 
surrounding it, as already mentioned. (See map, Pl. X.) The 
character of this depression is best understood when studying the 
question of the drowned valleys as a whole. The continental shelf 
extends 70 miles east of Trinidad.} 
') See U.S. Hydrographie Chart, No. 1010. 
