440 MEXICO, CENTRAL AMEPJCA, WEST INDIES. 



but no serious attempt was made to cultivate the land till after tlie American 

 War of Independence, when some loyalist planters removed with their slaves to 

 the archipelago. 



Physical Features. 



While the Bahamas remained in the power of the corsairs the true form of 

 the various groups necessarily remained unknown. But since the establishment 

 of legitimate trade their outlines have been revealed and reproduced in admirable 

 marine charts. The contour lines of all the clusters and of the submarine banks 

 on which they rest are now known in full detail. Taken as a whole the Bahaman 

 plateau may be compared to the island of Cuba, which it greatly exceeds in 

 extent. Like Cuba, it is an insular mass of great length, but relatively narrow, 

 fringed by countless reefs and indented by deep inlets. 



The geological formation is also the same, except that Cuba is already old 

 and increases but slowly, whereas the sister island is being built up under our 

 very eyes by the incessant work of the coral-builders. The land already above 

 water is all composed of whitish calcareous rocks fused in a homogeneous mass 

 differing in age alone from the ragged coralline reefs mingled with sands and 

 broken shells which line the beach. The rock grows continuously on its outer 

 or seaward face, where the structures of the animalculte rise gradually higher 

 and higher, and become consolidated by their very rupture, thanks to the 

 calcareous cement by which the broken fragments are again soldered together. 

 Thus the British frigate Severn, wrecked on a reef of the Turks grouj) in 1793, 

 is now completely encrusted with a rocky coating of still living coral. 



In the neighbourhood of the same islands, as well as at some other points 

 round the periphery of the plateau, certain reefs, known by the name of coral- 

 heads, affect the form of huge mushrooms shooting up from the depths of the 

 sea. The stems, from 30 to 50 feet high, with an average width of about 16 

 feet, support extensive heads or platforms 300 or 400 feet in circumference, which 

 are exposed at low water. Ebb and flow being very slight in these waters, the 

 polyps are able to build up their structures without much disturbance from the 

 waves. At last the stony piles coalesce together, leaving below them submarine 

 caves and galleries, where the water, rushing in, drives the confined air forward, 

 and reappears farther on in broad sheets of foam. Whipple relates that a 

 wounded whale escaped by plunging into one cavernous recess and emerging 

 some distance olï at the other end of the reef. 



Since the polyps have been at work the relative level of land and sea has 

 undergone little change, for the mean elevation of the islands above the Atlantic 

 tides scarcely exceeds 7 or 8 feet. In some the surface is slightly undulating, 

 or disposed in receding terraces with rocky escarpments indicating the old shore- 

 line. The whole system culminates in a hill in Cat Island, which is scarcely 

 400 feet high. 



But despite their low elevation above the surface, the islands present pro- 

 digious altitudes, measured from the ocean bed. In this respect the Bahamas 



