STRUCTURE OF THE TURKS ISLANDS 255 



the eastern islands rise. All the islands are of moderate elevation, 

 Cat Island displaying the greatest height of about 400 feet ; but their 

 average height would not amount to half this elevation, and large 

 areas of some islands are not removed many feet above the sea. 



Whilst viewed orographically the Bahamian banks are connected 

 at their western end with the Florida region and project at their 

 eastern end into the ocean's depths, they present a similar relation 

 with the Greater Antilles. This connection becomes more and more 

 dissevered as we proceed from west to east, depths of rather under 

 300 fathoms dividing the Great Bahama Bank from the north coast 

 of Cuba, whilst depths of 2000 fathoms and over separate the eastern 

 banks, on which the Turks and Caicos Islands lie, from the north 

 coast of Hispaniola. Trending eastward from the Turks Bank is the 

 line of the Mouchoir, Silver, and Navidad Shoals, which are sur- 

 rounded on the north, east, and south sides by depths of 2000 to 

 3000 fathoms. On the north side of the Bahamian archipelago the 

 submarine slopes descend to depths of 2000 fathoms a few miles 

 from the shore. 



Some curious considerations offer themselves when we reflect on 

 the present and past conditions of the Bahamas, of which the Turks 

 Islands form a part, considerations that have a bearing on the 

 origin of the geological structure and of the floral characters of the 

 whole region. It may be that in Miocene times, when the Florida 

 peninsula was under the waves, the Bahamas were the Laccadives 

 and the Maldives of the coral-reef region of the Atlantic. Dana in 

 his Corals and Coral Islands (p. 213) gives vent to a suspicion of this 

 kind ; but he did not follow it up, and contented himself with noting 

 the analogy between the eastern and western ranges of land on the 

 Great Bahama Bank and the opposite sides of the Maldive Group. 

 However, the coral reef makes a peremptory demand to be called 

 as a witness in this connection, and for this reason. Only in coral- 

 reef regions could we find the conditions that have produced an 

 archipelago, several hundred miles in length, consisting of relatively 

 low islands that are entirely composed of reef debris and calcareous 

 aeolian rocks. In a geographical sense the analogy with the above- 

 named archipelagos of atolls in the Indian Ocean is closer than 

 would at first appear. The Laccadives would represent the western 

 portion of the Bahamas, where the islands come into relation with 

 the adjacent continent, and the Maldives would stand for the free 

 oceanic eastern portion that protrudes into the ocean's depths. 



In the Bahamas we have an archipelago possessing hundreds of 

 islands, large and small; and yet along its length of 600 miles and 

 more there is not an island that is more than 400 feet above the sea, 

 the majority of them not exceeding half this elevation. Several of 

 the eastern islands rise from banks that are the flattened tops of 

 submarine mountains starting up some 12,000 feet above the ocean's 

 floor. Yet there is relatively little difference in the elevation of the 

 islands, and we find this small range in height along the length of 

 the archipelago. We have here the anomaly that so exercised 

 Darwin's mind in the case of the lines of living atolls in the Indian 

 and Pacific Oceans ; that is, a lofty range of submarine mountains, 



