146 CORAL-REEFS. 



horizontally or in area, and vertically or in depth, necessary 

 to have submerged every mountain, even the highest, 

 throughout the immense spaces of ocean interspersed with 

 atolls, will probably strike most people as a formidable 

 objection to my theory. But as continents, as large as the 

 spaces supposed to have subsided, have been raised above 

 the level of the sea, — as whole regions are now rising, 

 for instance, in Scandinavia and South America, — and as 

 no reason can be assigned, why subsidences should not have 

 occurred in some parts of the earth's crust on as great a 

 scale both in extent and amount as those of elevation, 

 objections of this nature strike me as of little force. The 

 remarkable point is that movements to such an extent should 

 have taken place within a period, during which the poly- 

 pifers have continued adding matter on and above the same 

 reefs. Another and less obvious objection to the theory will 

 perhaps be advanced from the circumstance, of the lagoons 

 within atolls and within barrier-reefs never having become 

 in any one instance during prolonged subsidences of a 

 greater depth than 60 fathoms, and seldom more than 40 

 fathoms ; but we already admit, if the theory be worth con- 

 sidering, that the rate of subsidence has not exceeded that 

 of the upward growth of the coral on the exterior margin ; 

 we are, therefore, only further required to admit, that the 

 subsidence has not exceeded in rate the filling up of the 

 interior spaces by the growth of the corals living there, and 

 by the accumulation of sediment. As this filling up must 

 take place very slowly within barrier-reefs lying far from the 

 land, and within atolls which are of large dimensions and 

 which have open lagoons with very few reefs, we are led to 

 conclude that the subsidence thus counterbalanced, must 

 have been slow in an extraordinary degree ; a conclusion 

 which accords with our only means, namely, with what is 



