THE PACIFIC OCEAN. 277 



(Meandnna), and flower-like Caryophilla, occupy 

 the bottom. In the shallow hollows of the reef, 

 Pocillojwra verrucosa, a species having short waved 

 plates or branches, is found: when alive it is a beau- 

 tiful object, being of a delicate pale crimson hue. 



Conflicting statements have been made respect- 

 ing the activity of the building processes going on 

 in the present age; some affirming that the reefs 

 have acquired no perceptible addition, either to 

 their height or extent, since they have been known; 

 others anticipating a speedy filling up of the Pacific 

 from their rapid growth. The truth seems to be, 

 that, while in some localities no change in extent 

 can be traced through many years, in others very 

 rapid enlargements are made. As showing the rate 

 at which coral grows under favourable circumstances, 

 Mr. Darwin mentions two or three interesting cases. 

 In the lagoon of Keeling Atoll, a channel was dug, 

 for the passage of a schooner built upon the island, 

 through the reef into the sea ; in ten years after- 

 wards, when it was examined, it was found almost 

 choked up with living coral. Dr. Allan, at Mada- 

 gascar, placed several masses of coral, of different 

 species, each weighing ten pounds, in the sea three 

 feet beneath the surface, where they were secured 

 from removal by stakes. This was in December; 

 and in the month of July following, they were found 

 nearly extending to the surface, immovably fixed to 

 the rock, and grown to several feet in length. A 

 ship in the Persian Gulf, in the course of twenty 

 months, had her copper encased with living coral to 

 the thickness of two feet. 



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