— 13 — 



Iiistcatl of the worJs // almosfc necessary" Mr. Darwin' 

 doubtless iiitciided, tliat wc sliould understand and adopt tlic 

 meuiiing of //absolutcly ncccssary", but from what has already 

 been, and yet remains to be said on tliis point, we shall not 

 be disposed to adopt his uecessity, not even so much as //al- 

 most." Having already told us very truly, that all his clas- 

 ses of reefs agree in structurc, even in the most minute details , 

 it seems to follow that there is no more difficulty to be en- 

 countered for understanding that of any one, than that of any 

 other. By supposing the sinking of the central land and the 

 upward growth of the coral ring to continue, uutil the former 

 had disappeared below the surface of the sea, and the other 

 reached to the level of low water tides, we should indeed have 

 a lagoon reef produced, but certainly no lagoon islands. 



X. »It will at once be evident, that a coral reef closely skirting the 

 sshorc of a continent, ■n-ould in like uianucr, aftcr each sabsidence, risc 

 » to the surface. Ia the intcrvcning space , the water always encroaching 

 »upon the land, would not a barrier reef necessarily be produced, sirai- 

 »lar to the one extending parallel to the coast of Aiistralia? Itis indeed 

 »but uncoiling one of those reefs, wliich emiiclc at a distance so many 

 •» islands." 



Would not a submarine prolongation of the most coast 

 wise ridge of Australia, or of New Caledonia, or ifs parallel 

 submarine ridges, be equally effective as the basements of 

 those coral reefs? Altho' coils are in most instances circles, 

 yet circles are not coils; but be that as it may, if the mere 

 straightening of a circular line, as we suspect it, is all the 

 specific difFerence between one class and another, then we can 

 see no necessity for getting up a difterence of classes. But 

 the why it is, or has been, that those barrier builders have 

 not, as have their brethren at the encircled island, formed or 

 finished with islands. Mr. Dauwin has not enabled us to un- 

 derstand. 



IX. »Thiis the tliree grcat classes of reef, lagoon, cncircling and banier 

 »arc conncctcd togcther by one theory. (1) 



(1) The rcmaiadcr of this paragraph need not be quoted, because we 

 SCO no necd for making the rcmarks whiüh it is brougUt to answer, 

 (J. C. 1{.) 



