CORAL REEFS, AND ISLANDS. 269 



planted apart on a sandbank, three feet deep at low- 

 water. Each portion weighed ten pounds, and was , 

 kept in its place by stakes. Similar quantities were 

 placed in a clump, and secured as the rest. This 

 was done in December, 1830. In July following 

 each detached mass was nearly level with the sea, at 

 low-water, quite immovable, and several feet long, 

 stretching as the parent reef, with the coast current 

 from north to south." 



Lieutenant Wellstead communicated the fact that 

 " in the Persian Gulf a ship had her copper bottom 

 encrusted, in the course of ^twenty months, with a 

 layer of coral tivo feet in thickness, which it required 

 great force to remove when the vessel was docked." 



The inhabitants at Keeling Island made with 

 crowbars a considerable channel through the reefs, 

 in which a schooner was floated out. In less than 

 ten years this channel was again almost choked up 

 with living coral, so that fresh cuttings would be 

 absolutely necessary before another vessel could pass 

 through. 



If these instances can be accepted as types, or as 

 approximations towards the determination of the 

 growth of coral, under ordinary circumstances and 

 conditions, then it can scarcely be maintained that 

 the growth of coral is always slow. 



The most popular of the older theories of the 

 formation of coral-atolls, was that which regarded 



