CORAL-REEFS. 77 



under certain circumstances. To this latter belief I am 

 led, by rinding that channels are almost universally present 

 within the fringing-reefs of those islands which have under- 

 gone recent elevatory movements; and this could hardly 

 have been the case, if the conversion of the very shallow 

 channel into land had not been counteracted to a certain 

 extent. 



A fringing-reef, if elevated in a perfect condition above 

 the level of the sea, ought to present the singular appear- 

 ance of a broad dry moat within a low mound. The 

 author 1 of an interesting pedestrian tour round the Mauritius 

 seems to have met with a structure of this kind : he says, 

 "J'observai que la, oil la mer &ale, independamment des 

 rescifs du large, il y a k terre une espece d' effoncement ou 

 chemin couvert naturel. On y pourrait mettre du canon," 

 etc. In another place he adds, " Avant de passer le Cap, 

 on remarque un gros banc de corail eleVe* de plus de quinze 

 pieds : c'est une espece de rescif, que la mer a abandonne* : 

 il regne au pied une longue flaque d'eau, dont on pourrait 

 faire un bassin pour de petits vaisseaux." But the margin 

 of the reef, although the highest and most perfect part, 

 from being most exposed to the surf, would generally 

 during a slow rise of the land be either partially or entirely 

 worn down to that level, at which corals could renew their 

 growth on its upper edge. On some parts of the coast-land 

 of Mauritius there are little hillocks of coral-rock, which are 

 either the last remnants of a continuous reef, or of low islets 

 formed on it. I observed two such hillocks between 

 Tamarin Bay and the Great Black River ; they were nearly 

 20 feet high, about 200 yards from the present beach, and 

 about 30 feet above its level. They rose abruptly from a 



1 Voyage a tlsle de France ; par un Officier du Roi> part i. pp. 192, 

 200. 



