3G2 THE PHYSICAL GEOGRAPHY OF THE SEA. 



A "Gulf stream" in wind which forms a current in the air as remark- 

 *^^ -''"■• able as that of the Gulf Stream is in the sea. This 



atmospherical Gulf Stream is in the southeast trade-winds of the 

 Atlantic. It extends from near the Cape of Good Hope, in a di- 

 rect line to the equator, on the meridian of Cape St. Eoque (Plate 

 VIII.). The homeward route from the Cape of Good Hope lies 

 in the middle of this vein ; in it the winds are more steady than 

 in any other part of the Atlantic. On the edges of this remark- 

 able aerial current the wind is variable and often fitful ; the home- 

 ward-bound Indiaman resorts to and uses this stream in the at- 

 mosphere as the European-bound American does the Gulf Stream. 

 It is shaded on the plate. 



678. These investigations, with their beautiful developments, 

 counteriroiscs. eagerly captivate the mind; giving wings to the 



imagination, they teach us to regard the sandy deserts, and arid 

 plains, and the inland basins of the earth, as compensations in the 

 great system of atmospherical circulation. Like counterpoises to 

 the telescope, which the ignorant regard as incumbrances to the 

 instrument, these wastes serve as make-weights, to give certainty 

 and smoothness of motion — facility and accuracy to the workings 

 of the machine. 



679. When we travel out upon the ocean, and get beyond the 

 Noi-maistateofthaat- inAucnce of the land upon the winds, we find our- 

 mosphere. sclvcs iu a field particularly favorable for studying 

 the general laws of atmospherical circulation. Here, beyond the 

 reach of the great equatorial and polar currents of the sea, there 

 are no unduly heated surfaces, no mountain ranges, or other ob- 

 structions to the circulation of the atmosphere — nothing to disturb 

 it in its natural courses. The sea, therefore, is the field for ob- 

 serving the operations of the general laws which govern the 

 movements of the great aerial ocean. Observations on the land 

 will enable us to discover the exceptions, but from the sea we 

 shall get the rule. Each valley, every mountain range and local 

 district, may be said to have its own peculiar system of calms, 

 winds, rains, and droughts. But not so the surface of the broad 

 ocean ; over it the agents which are at work are of a uniform 

 character. 



680. Rain-winds are the winds which convey the vapor from 

 Rain-winds. the sca, whcrc it is taken up, to other parts of the 



