THE VOYAGE OF THE BEAGLE 



491 



prise when travellers tell us of the vast dimensions of the 

 Pyramids and other great ruins, but how utterly insignificant 

 are the greatest of these, when compared to these moun- 

 tains of stone accumulated by the agency of various minute 

 and tender animals! This is a wonder which does not at 

 first strike the eye of the body, but, after reflection, the eye 

 of reason. 



I will now give a very brief account of the three great 

 classes of coral-reefs; namely, Atolls, Barrier, and Fringing- 

 reefs, and will explain my views 11 on their formation. Al- 

 most every voyager who has crossed the Pacific has ex- 

 pressed his unbounded astonishment at the lagoon-islands, or 

 as I shall for the future call them by their Indian name of 

 atolls, and has attempted some explanation. Even as long 

 ago as the year 1605, Pyrard de Laval well exclaimed, " C'est 



une merveille de voir chacun de ces atollons, environne d'un 

 grand banc de pierre tout autour, n'y ayant point d'artifice 

 humain." The accompanying sketch of Whitsunday Island 

 in the Pacific, copied from Capt. Beechey's admirable Voy- 

 age, gives but a faint idea of the singular aspect of an atoll: 

 it is one of the smallest size, and has its narrow islets united 

 together in a ring. The immensity of the ocean, the fury of 

 the breakers, contrasted with the lowness of the land and the 

 smoothness of the bright green water within the lagoon, can 

 hardly be imagined without having been seen. 



The earlier voyagers fancied that the coral-building ani- 



"These were first read before the Geological Society in May, 1837, and 

 have since been developed in a separate volume en the " Structure and 

 Distribution of Coral Reefs." 



