112 J. W. SPENCER — RECONSTRUCTION OF ANTILLEAN CONTINENT. 



now constitutes the Bahama islands and banks. The configuration here 

 indicates that formerly the Bahaman valley drained the northern side of 

 what is now the ridge underneath the Gulf Stream where it emerges from 

 the straits of Florida. This channel is entirely submerged to depths of 

 from 2,064* to 10,314 feet in a distance of 350 miles. Near its mouth 

 the fjord is bounded on one side by the plateau, rising 6,800 feet above 

 its floor, and on the other by the watershed between it and the Altamahan 

 fjord, which has also the great elevation of over 5,000 feet, although so 

 deeply submerged. The Abacan fjord (named from the adjacent island) 

 differs from the last three in that it passes between low islands, though 

 crossing the same subcoastal plateau. It extends eastward from a point 

 west of the Bahamas, where the depth is nearly 2,400 feet, with the trans- 

 verse ridges of the straits of Florida considerably higher. Thirty miles 

 eastward it is 5,688 feet below sealevel, and increases to a depth of over 

 10,000 feet south of Great Abaco island, where it joins another canyon- 

 like depression no less clearly indicated by the soundings. The Abacan 

 fjord is of particular interest as showing that the Gulf Stream has taken 

 possession of three different valleys. Its presence also indicates that 

 while the Gulf Stream has probably deepened the divide between the 

 northern and southern valley (deepest sounding, 2,064 feet), yet the val- 

 leys existed before the Gulf current, for, while eroding the higher cols, 

 the current tends to fill up the deeper channels, into the quieter waters 

 of which the sediments settle ; but the Abacan channel, not receiving the 

 Gulf Stream, except where crossed at its head, has not been filled by the 

 debris of the current-scour even in its upper reaches, thus suggesting 

 that this marine current has not made, though it may have modified, 

 the valley of the Floridian strait. 



The Androsan fjord is 4,500 feet deep at the head of the tongue of the 

 ocean and 8,940 feet near the mouth of the Abacan, below which the two 

 valleys are united and enter the oceanic embayment with a depth of 

 14,178 feet. Here the soundings indicate an interesting feature. Into 

 this embayment, which is 120 miles wide, there enter four great fjords 

 (Altamahan, Bahaman, Abacan and Androsan). The embayment is 

 bounded on the northern side by an island, now submerged to a depth 

 of about 4,000 feet, and in front of it there is another, rising to 5,000 feet 

 above the floor of this arm of the Atlantic basin. 



All of the submerged channels crossing the Blake plateau have directions 

 at right angles to the mountain ranges of the continent, and apparently 

 represent continuations of the existing rivers. There are also many short, 

 drowned canyons among the Bahamas and banks, but the soundings are 



* la latitude 21%'^, longitude 79)^° W., the channel has reached a depth of 3,882 feet, as shown in 

 an unpublished sounding of the Hydrographie OfiHce, 



