68 HARBOUR CONSTRUCTION. 



equal magnitude. One of these is turned south-westward into 

 the South Atlantic, while the other passes on to the West Indies 

 and Gulf of Mexico, whence it emerges, through the Strait of 

 Florida, as the Gulf Stream, and assumes a north-easterly 

 direction. It pursues this course towards the North Pole, by 

 way of the British Isles and the northern coast of Norway, 

 doubtless as a return current to compensate the loss caused by 

 the outflow, both as surface and under currents, of cold water 

 from the pole to the equatorial regions. 



It is worthy of note that the Equatorial Current, including 

 its continuation the Gulf Stream, alters its course in about the 

 same latitude and in the same direction as the prevailing winds ; 

 and, further, that the tracks of nearly all the memorable storms 

 recorded by Reid in his work on the "Law of Storms and 

 Variable Winds," coincide in a remarkable manner with the course 

 of the Equatorial Current and Gulf Stream. With few exceptions, 

 the direction taken by these storms appears to have been from 

 about east-south-east until between the twenty-fifth and thirtieth 

 parallels of north latitude, when they gradually assumed a more 

 northerly direction, and, on arriving at about 30 N. lat., they 

 began to trend away to the eastward, following very nearly the 

 course of the Gulf Stream, as before stated. 



It is well known, or at all events pretty generally believed, 

 that aerial currents and ocean currents act and react upon each 

 other ; and I am disposed to think that the heated waters of the 

 Gulf Stream cause an upcast aerial current along its course, 

 tending to draw to it any storm that may chance to come within 

 its influence. 



In some localities, where winds blow with great regularity 

 from particular quarters, temporary surface currents are set up 

 by them. These are very liable to be mistaken for constant 

 ocean currents if not observed for a sufficiently long period, and 

 serious mistakes in the design of harbour works may thus be 

 made. 



That wind cannot be looked upon as the only, or even 

 principal, current producing power, seems to be evinced by the 

 fact that currents often flow against prevailing winds. For 

 instance, the Agulhas current flows west against strong prevalent 

 westerly winds, and the south -going cold surface current out 

 of Baffin's Bay runs counter to the Gulf Stream and also to 

 prevailing winds ; indeed, it is common to find adjacent currents 



