(haciendados) owes its origin to the decomposition of some superficial beds of oxidated iron, mixed with silex and clay, or to a reddish sandstone* (* Sandstone and ferruginous sand; iron-sand?) superposed on limestone. The whole of this formation, which I shall designate by the name of the limestone of Guines, to distinguish it from another much more recent, forms, near Trinidad, in the Lomas of St. Juan, steep declivities, resembling the mountains of limestone of Caripe, in the vicinity of Cumana. They also contain great caverns, near Matanzas and Jaruco, where I have not heard that any fossil bones have been found. The frequency of 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 worked in several places on the east of Matanzas, at San Antonio de los Banos, where it contains sulphur, and at the Cayos, opposite San Juan de los Remedios. We must not confound with this limestone of Guines, 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 soundings 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.* (* M. Moreau de Jonnes has well distinguished, in his Histoire physique des Antilles Francoises, between the Roche a ravets of Martinique and Hayti, which is porous, filled with terebratulites, and other vestiges of sea-shells, somewhat analogous to the limestone of Guines and the calcareous pelagic sediment called at Guadaloupe Platine, or Maconne bon Dieu. In the cayos of the island of Cuba, or Jardinillos del 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 living.) MM. Chamiso and Guiamard have recently thrown great light on the formation of the coral islands in the Pacific. At the foot of the Castillo de in Punta, near the Havannah, on shelves of cavernous rocks,* covered with verdant sea-weeds and living polypi, we find