221 

 On Coral Beefs and Islands. By Jambs B. Jt)AirA. 



(Continued froni page 62.) 



Formation of Beefs, and Causes of their Features and (jreogra- 

 phical Distribution. 



An inquiry into the causes and origin of the features pre- 

 sented by coral reefs and islands, has led us to glance at the 

 nature of coral zoophytes, and at the effects of various agents 

 upon their development. The way has thus been prepared 

 for considering the bearing of these facts, and of other influ- 

 encing causes, on the growth of the coral plantation as a 

 whole. While, therefore, the preceding pages treat of zoo- 

 phytes as individual species, the following will relate to 

 those results which proceed from their accumulation, and 

 the causes which have determined the features and geo- 

 graphical distribution of reefs and island^.' ' 



1. Formation of Reefs.' 



Very erroneous ideas prevail respecting the appearance of 

 a bed or area of growing corals. The submerged reef is 

 often thought of as an extended mass of coral, alive uni- 

 formly over its upper surface, and, by this living growth, 

 gradually enlarging upward ; and such preconceived views, 

 when ascertained to be erroneous by observation, have some- 

 times led to scepticism with regard to the zoophytic origin 

 of the reef rock. Nothing is wider from the truth ; and this 

 must have been inferred from the descriptions already given. 

 Another glance at the coral plantation should be taken by 

 the reader, before proceeding with the explanations which 

 follow. 



Coral plantation and coral field, are more appropriate ap- 

 pellations than coral garden, and convey a juster impression 

 of the surface of a growing reef. Like a spot of wild land, 

 covered in some parts with varied shrubbery, in other parts 

 bearing only occasional tufts of vegetation over barren plains 

 of sand, here a clump of saplings, and there a carpet of 

 variously-coloured flowers — such is the coral plantation. Nu- 

 merous kinds of zoophytes grow scattered over the surface 



