AGASSIZ: BAHAMAS. 79 



An examination of the larger charts of this part of the Bahamas will 

 show the effect which subsidence has had in forming a number of boat 

 harbors and inlets on the shores of this cay. Some of them have twenty 

 feet of water, and are more or less protected by the patches of coral 

 reef growing between the cay and the edge of the bank. Upon these 

 patches the sea beats violently, forming two or three lines of breakers, 

 through which it is often impossible even for small boats to find their 

 way out. Similar sinks exist upon many parts of the Bahamas, one of 

 the most characteristic of which is Hurricane Hole, south of Andros 

 (Plate XI. Fig. 4). 



After leaving Green Turtle Cay, immediately along the sea face of the 

 Little Bahama Bank on our way south, we passed through great masses of 

 gulf-weed. There is little doubt that much of the Sargassum we meet 

 with in the Bahamas comes from the shores of the cays. It is found in 

 considerable profusion in many localities, and, while gi-owing vigorously 

 during the comparatively short season of calms, immense quantities are 

 torn off during gales or heavy seas, so that a fresh stock of Sargassum 

 must at all times be increasing the mass floating in the range of 

 the Gulf Stream and of the northern extension of the equatorial set. 

 How long it can thus float, and perhaps propagate by budding, is not 

 known. It is, however, a well known fact, that Sargassum torn off from 

 the rocks can be kept thriving for months in tanks or dishes. 



The slopes of the low shore hills of Great Abaco, as seen extending 

 southward from the anchorage at Green Turtle Cay, show in a most 

 characteristic way their seolian structure. The base of these hills is cut 

 off by low vertical cliffs which have been formed by the gradual wearing 

 away of the rocks by the sea. "We examined the shore of Great Abaco 

 at Black Point, pulling round it and landing inside on the sand beach 

 formed behind the spit. The rocks present the same seolian structure, 

 and are greatly worn by the breakers. The material back of the beach 

 is more in the amygduloid stage than in the marl stage. In thx-ee and 

 a half fathoms off the beach the bottom is somewhat more sticky than 

 the cleaner samples taken immediately on the beach. 



In our way out through "Whale Channel Cay we found all the islets 

 and rocks rounded off on the summits, the surface pitted and honey- 

 combed and eaten away at the base of the rocks. 



From the summit of the white cliff to the eastward of the landing on 

 Green Turtle Cay we could see the breakers on the outer coral reef, 

 which extends more or less parallel with the edge of the bank all the way 

 round its eastern edge in a nearly unbroken line. 



