OCR Text |
Show .ANNOTATIONS A D ADDITIONS. 135 beyond the Equator near the I land of St. Thomas. It gives at the same time a northwesterly direction to a part of the water of the South Atlantic, causing it to strike Cape St. Augustin, and to follow the coast of Guiana to beyond the mouth of the Orinoco, the Boca del Drago, and the coast of Paria. (Rennell, Investigation of the Currents of the Atlantic Ocean, 1832, pp. 96 and 136.) The 'New Continent, from the Isthmus of Panama to the northern part of Mexico, opposes a barrier to the farther continuance of this movement of the waters, and thus the current is constrained to assume a northerly course off V eragua, and thence to follow the windings of the coast of Costa Rica, Mosquito, Campeachy, and Tobasco. The waters which enter the Mexican Gulf between Cape Catoche of Yucatan and Cape San Antonio of Cuba, after completing a great rotatory movement or circuit, by Vera Cruz, Tamiagua, the mouth of the Rio Bravo del Norte, and that of the Mississippi, force their way northwards through the Bahama Channel, and re-issue into the open ocean. Here they form the well-known " Gulf Stream," a current or river of warm and rapidly moving water, flowing in an oblique or diagonal direction, carrying it farther and farther from the North American coast. Ships from Europe bound for thi"s coast, when uncertain in respect to their longitude, are enabled by this oblique direction of the current to direct their course, as soon as they reach the Gulf Stream, by observations of latitude only. The position of this great current was first indicated with accuracy . by Franklin, Williams, and Pownall. From the 41st degree of latitude, the river of warm water, which has been gradually diminishing in rapidity and increasing in breadth, turns suddenly to the east. It almost touches the southern edge of the great Newfoundland bank, where I found the greatest amount of difference between the temperature of the warm water of the Gulf Stream, and that of the waters resting on the banks and subjc<;:ted thereby to a cooling process. Before the stream reaches the westernmost of the Azores it divides into two branches, one of which, at least at certain seasons, advances towards Ireland and Norway, and the other towards the Canaries and the west coast of Africa. This Atlantic rotatory· movement (described by me more in detail in the first volume of my Voyage to the Equinoctial Regions), explains the |