CHAPTER IV. 



ON THE GROWTH OF CORAL-REEFS. 



In this chapter I will give all the facts which I have 

 collected, relating to the distribution of coral-reefs, — to 

 the conditions favourable to their increase, — to the rate 

 of their growth, — and to the depth at which they are 

 formed. 



These subjects have an important bearing on the theory 

 of the origin of the different classes of coral-reefs. 



Section First. 



On the distribution of coral-reefs, and on the conditions favourable to 



their increase. 



With regard to the limits of latitude, over which coral- 

 reefs extend, I have nothing new to add. The Bermuda 

 Islands, in 3 2° 15' N., is the point furthest removed from 

 the equator, in which they appear to exist; and it has 

 been suggested that their extension so far northward in 

 this instance is owing to the warmth of the Gulf Stream. 

 In the Pacific, the Loo Choo Islands, in lat. 27 N., have 

 reefs on their shores, and there is an atoll in 2 8° 30', 

 situated N.W. of the Sandwich Archipelago. In the Red 

 Sea there are coral-reefs in lat. 30 . In the southern hemi- 

 sphere coral-reefs do not extend so far from the equatorial 

 sea. In the Southern Pacific there are only a few reefs 



