202 



CURRENTS OF THE SHOAL. 



Pedro Keys, and South Key, all surrounded by dangerous 

 breakers. The depth is six or eight fathoms; but, in 

 advancing to the middle of the bank, along the line of the 

 summit, first towards the west and then towards the north- 

 west, the depth becomes successively ten, twelve, sixteen, 

 and nineteen fathoms. When we survey on the map the 

 proximity of the high lands of San Domingo, Cuba, and 

 Jamaica, in the neighbourhood of the Windward Channel, 

 the position of the island of Navaza, and the bank of Hor- 

 migas, between Capes Tiburon and Morant; when we trace 

 that chain of successive breakers, from the Vibora, by Baxo 

 Nuevo, Serranilla, and Quita Sueno, as far as the Mosquito 

 Sound, we cannot but recognize in this system of islands 

 and shoals, the almost-continued line of a heaved-up ridge, 

 running from N.E. to S.W. This ridge, and the old dyke, 

 which link, by the rock of Sancho Pardo, Cape San Antonio 

 to the peninsula of Yucatan, divide the great sea of the 

 West Indies into three partial basins, similar to those 

 observed in the Mediterranean. 



The colour of the troubled waters on the shoal of La 

 Vibora, has not a milky appearance like the waters in the 

 Jardinillos, and on the bank of Bahama; but it is of a dirty 

 grey colour. The striking differences of tint on the bank of 

 Newfoundland, in the archipelago of the Bahama Islands and 

 on La Vibora, the variable quantities of earthy matter sus- 

 pended in the more or less troubled waters of the soundings, 

 may all be the effects of the variable absorption of the 

 rays of light, contributing to modify to a certain point the 

 temperature of the sea. Where the shoals are 8 to 10 

 colder at their surface than the surrounding sea, it cannot 

 be surprising that they should produce a local change of 

 climate. A great mass of very cold water, as on the bank 

 of Newfoundland, in the current of the Peruvian shore 

 (between the port of Callao and Punta Pariiia*), or in 

 the African current near Cape Verd, have necessarily an 

 influence on the atmosphere that covers the sea, and on 



* I found the surface of the Pacific ocean, in the month of October, 

 1802, on the coast of Truxillo, 15'8 cent.; in the port of Callao, in 

 November, 15 '5*; between the parallel of Callao and Punta Parina, in 

 December, 19; and progressively, when the current advanced towards 

 the equator, and receded towards the W.N.W., 20'5 and 22 '3. 



