-1859] WRITINGS OF JOSEPH HENRY. 15 



whirl exists in this ocean, and in some seasons is at times 

 divided into two, giving rise to the peculiar currents of this 

 part of the earth's surface. Besides these great circular 

 streams, the water supplied by all the rivers emptying into 

 the Arctic basin, as well as that from all the precipitation 

 in this region, returns to the south in a current between 

 Europe and America, which as we shall hereafter see has 

 a very marked influence on the temperature of our coast. 

 A similar current, but more diffuse and less in amount, must 

 constantly flow from the Antarctic regions. In this view 

 we have adopted the hypothesis which ascribes the priifcipal 

 efiiect to the trade winds. A portion however will be due 

 to the currents produced by the heating of the water itself. 

 To illustrate the effect of these currents on the climate of 

 the United States, let us consider those of the North Atlantic 

 and North Pacific oceans, between which our continent is 

 situated. 



The great whirl in the North Atlantic, the western and 

 northern portions of which are known as the Gulf Stream, 

 passes southward down the coast of Africa, crosses the ocean 

 in the region of the equator, is deflected from the northern 

 portion of South America and the coast of Mexico along the 

 United States, and re-crosses the Atlantic at about the lati- 

 tude of 40°, to return into itself at the place where it started. 

 A portion however of this current (probably owing to the 

 configuration of the bottom) passes off" in a tangent to the 

 circumference of the great whirl and flows northward along 

 the coasts of Ireland and Norway. By this current the 

 heated waters of the equator are carried northward along the 

 eastern coast of the United States and precipitated upon the 

 shores of Northern Europe, giving the temperature of a south- 

 ern latitude even to North Cape, the extremity of Europe, 

 which would otherwise be as cold as Greenland. This stream 

 has less eff'ect upon the climate of the United States than 

 upon that of the western coast of Europe; first, because the 

 prevailing wind is from the west; and secondly, because be^ 

 tween our shores and the Gulf Stream the cold polar current 

 intervenes. 



