360 THE BEAUTIES OF NATURE CHAP, 
feet above the level of the water, and bear 
generally groups of tufted Cocoa Palms. 
It used to be supposed that these were the 
summits of submarine volcanoes on which the 
coral had grown. But as the reef-making 
coral does not live at greater depths than 
about twenty-five fathoms, the immense 
number of these reefs formed an almost 
insuperable objection to this theory. The | 
Laccadives and Maldives for instance — mean- 
ing literally the “lac of or 100,000 islands,” 
and the “ thousand islands’’ —are a series of 
such atolls, and it was impossible to imagine 
so great a number of craters, all so nearly of 
the same altitude. 
In shallow tracts of sea, coral reefs no 
doubt tend to assume the well-known circular 
form, but the difficulty was to account for 
the numerous atolls which rise to the surface 
form the abysses of the ocean, while the coral- 
forming zoophytes can only live near the 
surface. 
Darwin showed that so far from the 
ring of corals resting on a corresponding 
ridge of rocks, the lagoons, on the contrary, 
