CORALS. 141 



Of reptiles, horrent as ]Medusa's snakes, 



Covered the bald-pate reef; then all was life, 



And indefatigable industry ; 



The artisans were twisting to and fro, 



In idle-seeming convolutions ; yet 



They never vanished with the ebbing surge, 



Till pellicle on pellicle, and layer 



On layer, was added to the growing mass. 



Ere long the reef o'ertopped the spring-flood's height, 



And mocked the billows when they Icap'd upon it. 



Unable to maintain their slippery hold. 



And falling down in foam -wreaths round its verge. 



Steep were the flanks, with precipices sharp. 



Descending to their base in ocean gloom. 



Chasms few and narrow and irregular, 



Form'd harbours, safe at once and perilous, — 



Safe for defence, but perilous to enter, 



A sea-lake shore amid the fossil isle, 



Reflecting in a ring its clifi^s and caverns, 



With Heaven itself seen like a lake below." 



Yet it is incorrect to suppose that the Coral Islands, as 



they are called, are composed entirely of Corals from their 



very foundations. It has been well advanced, and almost 



proved, that the islands were originally volcanic mountains 



rising to a great height above the sea. Eound the base of 



the mountain these Zoophytes commenced their operations, 



and fringed the edge at low -water mark. By degrees, the 



island began to sink, and the fringe of Corals would sink 



