64 WRITINGS OF JOSEPH HENRY. [1855- 



formed as to its climate. The North American continent 

 extends across nearly the whole breadth of the nominal tem- 

 perate zone, and has an average width of more than fifty de- 

 grees of longitude. The general direction of the eastern 

 coast of the United States lies in a great circle passing 

 through Great Britian. Hence, a ship, while sailing along 

 this coast, is on its direct route to the British Isles. This 

 fact — which is not clearly exhibited on the flat surface of 

 a map, but is shown on the convex surface of a globe — has 

 a bearing, not only on commerce, but also on the direction 

 of the Gulf Stream, which conforms to the general direction 

 and sinuosities of the coast. It will be seen by the map,* 

 (to which frequent reference is here made), that the eastern 

 coast of the United States exhibits three great concave curv- 

 atures ; the first commencing at the extremity of Florida, 

 and extending to Cape Hatteras; the second, from Cape 

 Hatteras to Cape Cod ; and the third, from Cape Cod to Cape 

 Sable. These broad ocean bulgings, or bays, have a marked 

 influence on the cold polar current which descends along 

 the coast, and also, as has been shown by Professor Bache, on 

 the great tide-wave of the Atlantic ocean, as it approaches 

 our shore. At the southern extremity of the United States 

 is the great elliptical basin containing the perpetually 

 heated waters of the Gulf of Mexico, an enormous steaming 

 cauldron continually giving off" an immense amount of va- 

 por which, borne northward by the wind of the southwest, 

 gives geniality of climate and abundant fertility to the east- 

 ern portion of our domain. On the western side of the con- 

 tinent the coast presents, as a whole, an outline of double 

 curvature, principally convex to the west in that part which 

 is occupied by the United States, and concave further north. 

 These bends of the coast-line and of the adjacent parallel 

 mountain ridges affect the direction of the winds in this quar- 

 ter and consequently of the ocean currents. The Gulf of 

 California at the south, between the high mountains of the 

 peninsula of that name and those of the main land, must also 

 materially modify the direction of the wind in that region. 



*fSee Map, at page 72.] 



