-1859] WRITINGS OF JOSEPH HENRY. 285 



extended circuit is completed in about three years. In the 

 Atlantic Ocean a branch is sent off from this circuit, which 

 passes northward, impinges on the western coast of Europe, 

 and probably skirts the whole circuit of the polar basin, from 

 which it passes out on the west side at Behring's Straits. 



Two similar systems of currents exist in the Pacific Ocean; 

 that in the northern hemisphere passing from Central 

 America along the equator to the continent of Asia, is 

 deflected northward along the coasts of China and Japan, 

 and returns to the equator along the western coast of North 

 America. 



Besides these great circuits from the equator, cold currents 

 descend from the polar basin. One of these is represented 

 by the arrows with double barbs between the Gulf Stream 

 and the eastern coast of the United States; and a similar 

 one descends along the coast of China between it and the 

 Gulf Stream of that region. These are in part derived from 

 the water which is discharged into the polar basin from the 

 several rivers of the north, and probably in part due to a 

 return portion of the equatorial currents. They skirt the 

 eastern shores of the continents, because currents from the 

 north (on account of the rotation of the earth) tend to move 

 westward, while those from the south tend to move eastward. 



The effect which these great currents of the ocean, (evi- 

 dently the natural results of the system of winds which we 

 have described,) produce on the climate of the United States, 

 compared with that of Europe, can readily be appreciated. 

 The elevated temperature of the water in the Gulf of Mex- 

 ico, (higher than that of the water in almost any other 

 part of the globe,) is retained by the Gulf Stream until it 

 reaches the shores of the polar basin. The southwest winds 

 which accompany and blow over the Gulf Stream share 

 its temperature, and impart their warmth and moisture to 

 Western Europe, giving it a climate far more genial than 

 would be due to the latitude. The southwest and west- 

 erly winds which prevail over the surface of the United 

 States serve to bear the heat of the Gulf Stream from our 

 coast, and even when an easterly wind is produced by local 



