On the morning of the 11th March we visited Cayo Flamenco. I found the latitude 21 degrees 59 minutes 39 seconds. The centre of this island is depressed and only fourteen inches above the surface of the sea. The water here is brackish while in other cayos it is quite fresh. The mariners of Cuba attribute this freshness of the water to the action of the sands in filtering sea-water, the same cause which is assigned for the freshness of the lagunes of Venice. But this supposition is not justified by any chemical analogy. The cayos are composed of rocks, and not of sands, and their smallness renders it extremely improbable that the pluvial waters should unite in a permanent lake. Perhaps the fresh water of this chain of rocks comes from the neighbouring coast, from the mountains of Cuba, by the effect of hydrostatic pressure. This would prove a prolongation of the strata of Jura limestone below the sea and a superposition of coral rock on that limestone.* (* Eruptions of fresh water in the sea, near Baiae, Syracuse and Aradus (in Phenicia) were known to the ancients. Strabo lib. 16 page 754. The coral islands that surround Radak, especially the low island of Otdia, furnish also fresh water. Chamisso in Kotzebue's Entdekkungs-Reise volume 3 page 108.) It is too general a prejudice to consider every source of fresh or salt water to be merely a local phenomenon: currents of water circulate in the interior of lands between strata of rocks of a particular density or nature, at immense distances, like the floods that furrow the surface of the globe. The learned engineer, Don Francisco Le Maur, informed me that in the bay of Xagua, half a degree east of the Jardinillos, there issue in the middle of the sea, springs of fresh water, two leagues and a half from the coast. These springs gush up with such force that they cause an agitation of the water often dangerous for small canoes. Vessels that are not going to Xagua sometimes take in water from these ocean springs and the water is fresher and colder in proportion to the depth whence it is drawn. The manatees, guided by instinct, have discovered this region of fresh waters; and the fishermen who like the flesh of these herbivorous animals,* find them in abundance in the open sea. (* Possibly they subsist upon sea-weed in the ocean, as we saw them feed, on the banks of the Apure and the Orinoco, on several species of Panicum and Oplismenus (camalote?). It appears common enough, on the coast of Tabasco and Honduras, at the mouths of rivers, to find the manatees swimming in the sea, as crocodiles do sometimes. Dampier distinguishes between the fresh-water and the salt-water manatee. (Voyages and Descr. volume 2) Among the Cayos de las doce leguas, east of Xagua, some islands bear the name of Meganos del Manati.)