380 OBSERVATIONS ON THE CURRENTS. 



Pillsbury, U.S.N., concludes that the Gulf Stream receives its water from 

 the Atlantic, partly by means of the current driven by the force of the S.E. 

 Trade Winds along the N.E. coast of South America, and partly by the 

 current from the N.E. Trades. The water, as a current, flows through the 

 passages between the Windward Islands, only, and not through the Ane- 

 gada, Mona, or Windward Passages. Not all the water entering the 

 Caribbean as described flows the length of that sea as a Current, but a 

 portion of it returns to the Eastward through the passages, usually as an 

 under-current. In addition, there is a large body of water thrown by the 

 waves into the Caribbean Sea through all the passages. The Current found 

 along the coast, between Trinidad and Cura9ao, is chiefly produced by the 

 escape of water thrown there by the waves, no large body permanently 

 entering the sea through the passage South of Grenada. The flow of water 

 across the Caribbean Sea is of the same character as that found outside 

 the islands, a scarcely perceptible current on the surface at first, but in- 

 creasing in its velocity farther West. 



The water thus accumulated in the Western part of the Caribbean Sea 

 escapes into the Gulf of Mexico, raising its surface level above that of the 

 Atlantic. The reported difference of about 40 inches in level between the 

 Gulf of Mexico, at Biloxi, and Sandy Hook, is probably largely in excess 

 of the actual difference, though it is probably many inches. The evidence 

 is that the small periodic changes of level of the Gulf of Mexico (0-3 to 

 041 foot) follow the changes in the Trade Winds, the highest level coming 

 at the time when the winds are throwing the greatest amount of water 

 into the Caribbean Sea, and also that the yearly variation in the Stream's 

 velocity follows the change in the level of the Gulf. 



Lieutenant Pillsbury continues :— " The average of all the Westerly flow 

 between the islands, from St. Vincent to Antigua, gives a volume equal to 

 about one-half that found in the narrowest part of the Straits of Florida. 

 What, then, can account for the other half? I am convinced that it is 

 the water thrown to leeward by the waves. Once in the Caribbean Sea, 

 every wave formed gives the surface current an additional push by its 

 momentum, so that by the time the part S.W. of Jamaica is reached, the 

 flow has greater velocity than in any of the passages between the islands." 

 (365.) In previous pages, describing the Equatorial Currents, it was 

 shown (302) to (317), pp. 343 to 352, that the united streams of the Northern 

 Equatorial Drift and the much more powerful stream from the South 

 Equatorial regions, when passing Cape San Roque and the Northern coast 

 of Brasil, have a breadth of not less than 2,000 to 2,200 miles, and these 

 flow with a velocity varying at times from 60 to 80 miles per day in the 

 Southern part, to 10 or 15 miles in the Northern part of the drift. This 

 Equatorial stream, which has a mean annual temperature of 77-6=' (varjung 

 between 72-5° and 81-4°) on the Eastern or African side, and increasing to 

 80-6° (from 79-7° to 84-2°) on the American side, covers an area of not less 

 than 6,400,000 square geographical miles of Tropically heated water. The 

 whole of this moving surface impinges on the Eastern face of the Caribbee 

 Islands, and here another difldculty awaits us. The line of islands diminish 

 the water-way, the openings between Barbuda and Trinidad being in tha 

 aggregate not 230 miles in width, or less than one-half of the range. So 



