166 GEOLOGY OF CTTBA. 



caverns in which the pluvial waters accumulate, and where 

 small rivers disappear, sometimes causes a sinking of the 

 earth. I am of opinion that the gypsum of the island of 

 Cuba belongs, not to tertiary, but to secondary soil ; it is 

 workH. in several places on the east of Matanzas, at San 

 Antoi i de los Banos, where it contains sulphur, and at the 

 Cayos, opposite San Juan de los Eemedios. We must not 

 confound with this limestone of Grumes, sometimes porous, 

 sometimes compact, another formation so recent, that it 

 seems to augment in our days. I allude to the calcareous 

 agglomerates, which I saw in the islands of Cayos that 

 border the coast between the Batabano and the bay of 

 Xagua, principally south of the Cienega de Zapata, Cayo 

 Buenito, Cayo Flamenco, and Cayo de Piedras. The sound- 

 ings prove that they are rocks rising abruptly from a bottom 

 of between twenty and thirty fathoms. Some are at the 

 water's edge, others one-fourth or one-fifth of a toise above 

 the surface of the sea. Angular fragments of madrepores, and 

 cellularia from two to three cubic inches, are found cemented 

 by grains of quartzose sand. The inequalities of the rocks 

 are covered by mould, in which, by help of a microscope, we 

 only distinguish the detritus of shells and corals. This 

 tertiary formation no doubt belongs to that of the coast of 

 Cumana, Carthagena, and the Great Land of Guadaloupe, 

 noticed in my geognostic table of South America.* MM. 

 Chamiso and G-uiamard have recently thrown great Light 

 on the formation of the coral islands in the Pacific. At 

 the foot of the Castillo de la Punta, near the Havannah, 

 on. shelves of cavernous rocks,f covered with verdant sea- 



* M. Moreau de Jonnes has well distinguished, in his Histoire phy- 

 sique des Antilles Fran$oises, between the "Roche a ravets" of Martinique 

 and Hayti, which is porous, filled with terebratulites, and other vestiges 

 of sea-shells, somewhat analagous to the limestone of Guines and the cal. 

 careous pelagic sediment called at Guadaloupe " Platme," or " Ma9onne 

 bon Dieu." In the " cayos" of the island of Cuba, or " Jardinillos deJ 

 Rey y del Reyna," the whole coral rock lying above the surface of the 

 water, appeared to me to be fragmentary, that is, composed of broken 

 blocks. It is, however, probable, that in the depth it reposes on masses 

 of polypi still lining. 



t The surface of these shelves, blackened and excavated by the waters, 

 presents ramifications like the cauliflower, as they are observed on th< 

 currents of lava. Is the change of colour produced by the watejrs owing 



