480 CURRENTS AND WHALING. 



and rheumatism, and the health of Europeans is less affected than at 

 other seasons, because the climate is then less dissimilar than usual to 

 their own. 



"The comparative unhealthiness of Prince's Island to that of St. 

 Thomas's, and of both to Anno Bon, as the residence of Europeans, 

 has been frequently and particularly noticed by Portuguese authori- 

 ties, and is universally recognised at Prince's Island and at St. 

 Thomas's. It may be a sufficient explanation to remark, that Anno 

 Bon is always surrounded by the Equatorial Current ; Prince's always 

 by the Guinea Current; and that the position of St. Thomas's is 

 intermediate, and its climate is occasionally influenced by both. In 

 tropical climates, a very few degrees of temperature constitute an 

 essential difference in the feelings of the natives, and in the health of 

 Europeans." 



In taking a general view of the facts which have been stated, it 

 will appear that, towards the western sides of the North and South 

 Atlantic, of the North and South Pacific, and of the Indian Oceans, 

 streams of heated water, making their way from low to high latitudes, 

 prevail. These in the two northern oceans become easterly, setting 

 towards the opposite continents, causing, beyond all question, the 

 comparatively equable and elevated temperature that is found on their 

 western coasts, and which so peculiarly distinguishes the climate of 

 the British Islands. To keep up the equilibrium of the ocean, the 

 body of water thus thrown from the equator towards the poles, must, 

 after being cooled and rendered more dense in the higher latitudes, 

 return towards the equator ; and the mode in which at first sight it 

 might be expected to do this is by currents wholly submarine. But 

 the influence of the returning water is felt at the surface also, forming 

 the surface polar streams, of which we have spoken. Those which 

 come from the great body of ocean in the southern hemisphere are 

 directed upon the projecting points of the continents and great islands, 

 Cape Horn, the Cape of Good Hope, Cape Leeuwin, &c, where as a 

 general rule, they are divided into two branches. The easternmost of 

 these meet the equatorial streams, of which I have spoken, whose 

 direction they change, modifying or checking their progress towards 

 the poles, and forming what I have termed the nuclei. In the North 

 Atlantic, we have seen that a part at least of the North Polar Stream 

 divides upon Cape Finisterre, passes into the Bay of Biscay, assuming 

 the form of a surface current allied to an eddy, called the Rennell 

 Current, while its main branch pursues its southern course along the 

 coast of Portugal, and finally again becomes wholly submarine. 



On the western side of the North Atlantic, in the higher latitudes, 



