— 1-1 — 



Wc have scon, tliat tlicre is no ground in fuct, al- 

 tho' some such may to Mr. Dauwin's fancy have appeared 

 needful, for maldng more than one class of reefs, and there- 

 fore no difficulty in connecting them on any theory, as well , 

 as OU the facts of any special instance. 



XII. »I slionld perliaps have entered bcfore into tlie oonsiJcralion of 

 »one apparcnt difficulty in the oii^ia of lagoon islands. It may be snid 

 j> that, granting the theory of subsidence, a mere circular óUc of coral 

 »would bc formed and a cup shaped mass. To this the rcply is, that 

 »In the first place, even in reefs closely fiinging the land, the corals do 

 »not grow on the shore itself, but leave a shal!o-\v channel, secondly, tho 

 3>strong and vigorous species, which aloiic build a solid reef, are never 

 » found withiu the lagoon, they only flourish amiJst the foam oftliencvcr 

 «dring brcakers. Neverthcless the more delicate corals tho' checked by 

 «several canses, such as strong tides and depo^its of sand, do constantly 

 » tend to fill up the lagoon, but the process must become slower and slo- 

 xwer, as the water in the shallow cxpanse is rendcrcd subject to acci- 

 » dental impurities. Ancurious instance of this happened at Keeling (the Cocos) 

 »Island, wherc a heavy tropical storm of rain killed nearly all the fish ( l_) 

 » When the coral at last has filled up the lagoon to the height of lowcst 

 » water at spring lides, which is the extreme limit possible, how afterwards 

 »i3 the work to be completed? There is no high land whence sediment can 

 »bc pourcd down and the dark blue colour of the ocean bespeaks its 

 » purity. The wind carrying calcareous dust from the outer coast is the 

 »only agent, which can finally convert the lagoon island into solid land, and 

 »how slow must that process be!" 



Mr. Darwin's explanation of the apparent difficulty is, 

 like the difficulty itself 'apparent, but nothing more. That 

 which not only //may" but must //be said" is what has been 

 said already. How does the reef, whether disc, or cup, or saucer 

 shaped, obtain an island to be laid on it's top , and there kept 

 abovc the level of the sea, whilst the foundation of the reef, 

 is undcrgoing the process of subsidence? but no reply to this 

 qucstion has Mr. Darwin found convenient to furnish. His 



(1) Not nearly all, but pcrhaps, nearly one in a hundred thousaud. 



To have » killed nearly all" would have requircd such »a storm of 



raiu" us has not, so far as wc know, fallcn from the sky, siuce the 

 'juc that Itiuuuhcd NüAu's ark. (J. C 11.). 



