118 THEORY OF THE FORMATION Ch. V. 



three loops, together sixty miles in length ; or like 

 Kimsky KorsacofF, narrow, crooked, and fifty-four miles 

 long ; or like the northern Maldiva atolls, made up of 

 numerous ring-formed reefs, placed on the margin of a 

 disk, — one of which disks is eighty-eight miles in 

 length, and only from ten to twenty in breadth ? A 

 further difficulty on this theory of the origin of atolls 

 arises from the necessary assumption of so large a 

 number of immense craters crowded together beneath 

 the sea. But, as we shall presently see, a greater diffi- 

 culty is involved, namely, that all these craters must 

 lie within nearly the same level beneath the sea. 

 Nevertheless, if the rim of a crater afforded a basis 

 at the proper depth, I am far from denying that a 

 reef like a perfectly characterized atoll might not be 

 formed on it. Some such, perhaps, now exist; but 

 it is incredible that the greater number could have 

 thus originated. 



An earlier and better theory was proposed by 

 Chamisso : ! he supposes that as the more massive kinds 

 of corals prefer the surf, the outer portions of a reef will 

 first reach the surface and consequently form a ring. 

 I remarked in the third chapter that a reef, growing on 

 a detached bank, would tend to assume an atoll-like 

 structure ; if, therefore, corals were to grow up from a 

 bank some fathoms submerged in a deep sea, having 

 steep sides and a level surface, a reef not to be dis- 

 tinguished from an atoll might be formed ; and I 



1 Kotzebue's First Voyage, vol. iii. p. 831. 



