136 



humboldt's cub a. 



one of which contains the great caverns of Matanzas 

 and the other is daily augmented "by the accumula- 

 tion of fragments of coral and quartz sand. The 

 latter of these formations seems to rest on the south 

 part of Cuba, sometimes on the Giiines (jurassic) 

 limestone, as in the Jardinillos, and at others (toward 

 Cape Cruz) immediately upon the primitive rock. 

 In the Lesser Antilles the coral has covered the 

 volcanic products. 



Many of the cays of Cuba contain fresh water, and 

 I have found excellent water in the centre of Cay de 

 Piedras. When we remember how extremely small 

 these islands are, we can hardly believe that those 

 ponds of fresh water are rain water that has not 

 evaporated. Perhaps they arise from a submarine 

 communication between the limestone formation of 

 the shore, and that which has served as a base for 

 the collection' of the lithophites : so that the fresh 

 water of Cuba rises by hydrostatic pressure through 

 the coral rock of the cays, as is the case in the bay 

 of Jagua, where fountains spring forth in the salt 

 water, and are the resort of the Manatf. 



East of Havana the secondary formations are 

 traversed by Syenite and Euphotide rocks, grouped 

 in a singular manner. The southern side of the bay, 

 as well as the northern (the hills of the Morro and 

 Cabana), are of jurassic limestone ; but on the east- 



