204: J. S. Gardiner — Origin of Coral Reefs. 



It is not mj intention to discuss tlie formation of coral reefs 

 at any length, or to give precise references to the great pioneer 

 work of Charles Darwin and James D. Dana, so greatly in 

 advance of its time, to the fresh considerations and opinions 

 ably put forward by Muri-ay, to the views of Semper, Louis 

 Agassiz and Wharton, and finally to the determined work of 

 Alexander Agassiz during the last twenty years. Such refer- 

 ences will be found in that beautiful series of publications, 

 which the latter authority has given to the world, from the 

 Museum of Comparative Zoology of Harvard College. It 

 suffices to remark that, while it may be that some i^eefs really 

 owe their existence to the subsidence of the land round which 

 they originally formed only a fringe, the great mass of facts, 

 that has been collected in the last twenty years, points out 

 clearly and decidedly that such a method of formation can 

 never have been anything else but rare and altogether excep- 

 tional. Elevated reefs, which have proved to be extremely 

 numerous in coral reef regions, give no evidence of the very 

 considerable thickness which such a view postulates, and the 

 examination of the existing atolls and reefs has shown that 

 such a conception is unnecessary to explain any of their condi- 

 tions and is absolutely opposed to many. In some places, 

 notably some reefs of Fiji, the formations in progress are as 

 yet mere skins on the surfaces of older elevated limestone and 

 volcanic rocks, which have been cut down by denudation and 

 erosion to the level of the sea. Elsewhere, no doubt, and this 

 more particularly in the less open seas, reef foundations have 

 been built up to the recpisite depths by the accretion of the 

 remains of organisms, both pelagic and other, on submarine 

 mountains and elevations, or where the currents are such as to 

 especially bring about a deposition of material. Again, sub- 

 marine eruptions have thrown up mounds on the ocean floor, 

 perhaps to be built up further by organisms, perhaps of the 

 requisite depth, or perhaps to form islands, the latter of loose 

 cinders and ash, themselves to be cut down and form wide 

 plateaus on which reefs have subsequently arisen. A prima 

 facie example of this method is seen in that line of coral atolls, 

 the Gilbert and Ellice Groups, which seems to indicate a line 

 of weakness of the earth's crust. 



It is improbable, considering the diversified conditions of 

 the earth along the coral reef belt, that any one explanation 

 will be found to be of general applicability. Certainly no one, 

 nor indeed all of the above views, taken together, can serve to 

 explain the method by which the foundations of the Maldive 

 reefs were formed. The greater part of the Maldive Group 

 arises on an immense plateau lying at a depth of about 200 

 fathoms in a sea' of over 2000 fathoms. At the same time this 



