134 



humboldt's cuba. 



principally on Cay Bonito, Cay Flamenco, and Cay 

 de Piedras. By the soundings, we know that these 

 are rocks rising precipitously twenty or thirty 

 fathoms from the bottom. Some are level with the 

 sea. and others rise from one and a half to two feet 

 above the surface. Sharp fragments of white coral 

 and shells (cellularia), two or three cubic inches in 

 size and cemented with grains of quartz-sand, are 

 there found. All the inequalities of these rocks are 

 covered with made earth, in which, with a lens, we 

 can distinguish nothing but detritus of shells and 

 coral. This tertiary formation corresponds, without 

 a doubt, to that of the coasts of Cumana, Oarthagena, 

 and the Gran Terre de la Guadalupe, of which I 

 have spoken in my geognostic view of South America. 



Messieurs Ohamisso and Guaimard have lately 

 thrown much light upon the formation of the coral 

 islands of the southern seas. "While we see at 

 Havana, at the foot of the Punta fort, upon the 

 shore of cavernous rocks, 1 covered with verdant 



1 The surface of these shores, blackened and worn by the waves, 

 presents conical ramifications such as are found in lava currents. 

 The change of color caused by the waters is the effect of manganese, 

 the presence of which is known from the detritus. As the sea enters 

 the fissures of the rock and a cavern at the base of the Morro Castle, 

 it compresses the air and forces it out with an extraordinary noise, 

 which explains the phenomenon of the roaring banks so well known 



