272 PHYSIOGNOMY OF PLANTS. 



and Peru are washed by a cold current coming from the south and 

 turning to the westward off Punta Parina, the temperature of which 

 I found, in 1802, to be only 12.5 Reaumur (60.2 Fahr.), while 

 the undisturbed adjacent masses of water were from 22 to 23 

 Reaumur (81. 5 to 83. 8 Fahr.); and there are also among the G-a- 

 lapagos small currents running between the islands, having a tem- 

 perature of only 11. 7 Reaumur (58.2 Fahr.). But these lower 

 temperatures do not extend farther to the north along the shores of 

 the Pacific, and are not found upon the coasts of Guayaquil, Guati- 

 mala, and Mexico ; nor does a low temperature prevail at the Cape 

 de Verde Islands on the West Coast of Africa, or at the small islands 

 of St. Paul (St. Paul's rocks), or at St. Helena, Ascension, or San 

 Fernando Noronha which yet are all without coral reefs. 



While this absence of coral reefs appears to characterize the west- 

 ern coasts of Africa, America, and Australia, on the other hand such 

 reefs abound on the eastern coasts of tropical America, of Africa, on 

 the coasts of Zanzibar and Australia, and on that of New South 

 Wales. The coral banks which I have chiefly had opportunities of 

 observing are those of the interior of the Gulf of Mexico, and those 

 to the south of the Island of Cuba, in what are called the " Gardens 

 of the King and Queen" (Jardines y Jardinillos del Rey y de la 

 Reyna). It was Columbus himself who, on his second voyage, in 

 May 1494, gave that name to this little group of islands, because 

 the agreeable mixture of the silver-leaved arborescent Tournefortia 

 gnapholoides, flowering species of Dolichos, Avicennia nitida, and 

 mangrove hedges, gave to the coral islands the appearance of a group 

 of floating gardens. "Son Cayos verdes y graciosos llenos de arbo- 

 ledas," says the Admiral. On the passage from Batabano to Trini- 

 dad de Cuba, I remained several days in these gardens, situated to 

 the east of the larger island, called the Isla de Pinos, which is rich 

 in mahogany trees : my stay was for the purpose of determining the 

 longitude of the different keys (Cayos). The Cayo Flamenco, Cayo 

 Bonito, Cayo de Diego Perez, and Cayo de Piedras, are coral islands 

 rising only from eight to fourteen inches above the level of the sea. 

 The upper edge of the reef does not consist simply of blocks of dead 

 coral ; it is rather a true conglomerate, in which angular pieces of 

 coral, cemented together with grains of quartz, are embedded. In 



