James D. Dana, Esq., on Coral Beefs and Islands, 33 



Quits {Euphonia Jamaica)^ equally devoted admirers of a ripe 

 sour sop or custard-apple, accompany his loud notes with 

 strains of their own, full of soft warbling music. And the 

 most minute of birds, the tiny Vervain Humming bird {Mel- 

 lisuga humilis), not larger than a school-boy's thumb, utters a 

 song so sweet, but of sound so alternated withal, that you 

 wonder who the musician can be, and are ready to think it 

 the voice of an invisible fairy ; when presently you see the 

 atom of a performer perched on the very topmost twig of a 

 mango or orange tree, his slender beak open and his spangled 

 throat quivering, as if lie would expire his little soul in the 

 effort. — P. V. Gosse, Jamaica. 



( To be continued in our next Number.) 



I. Coral Beefs and Islands, II. The Structure, Growth, 

 and Habits of Coral Zoophytes. By JAMES D. Dana, Esq., 

 Naturalist to the American Exploratory Expedition. 



1. General Features of Coral Beefs and Islands. 

 The general features of reefs and coral islands have often 

 been delineated by travellers, and are probably almost as 

 familiar to the reader as the scenes of the land around us. 

 Yet a few brief remarks on this subject will not be out of 

 place here as preliminary to our observations on the struc' 

 ture, growth, and habits of coral zoophytes. 



Coral Beefs. — A wide platform of rock covered with the 

 sea, except at low tide, borders most of the high islands of 

 the Pacific. It is a vast accumulation of coral, based upon 

 the bottom in the shallow waters of the shores. This bank 

 or table of coral rock, is of varying width, from a few hundred 

 feet to a mile or more ; and, although the surface is usually 

 nearly flat, it is often intersected by irregular boat-channels, 

 or occasionally encloses large bays, affording harbour pro- 

 tection to scores of ships. In very many instances the reef 

 stands at a distance from the shores like an artificial mole, 

 leaving a wide and deep channel between it and the land ; and 

 within this channel are other coral reefs, some in scattered 

 patches, and others attached to the shore. The inner reef in 

 these cases, is distinguished as the fringing reef and the 

 outer as the barrier reef The sea rolls in heavy surges 

 against the outer margin of the barrier ; but the still waters 



VOL. LTI. NO. cm. — JANUARY 1852. 



