§ 123-125. THE GULF STREAM. 4| 



123. Now if this explanation as to the course of the Gulf Stream 



Herschei's theory and its eastwaid tendency hold good, a current set- 

 not consistent with . ~ , ,1, ti ti -, -, , r, -, ^ 



known facts. ting iroiTi the noith toward the south should (§ 103) 



have a westward tendency. It should also move in a circle of 

 trajection, or such as would be described by a trajectile moving 

 through the air without resistance and for a great distance. Ac- 

 cordingly, and in obedience to the propelling powers derived 

 from the rate at which different parallels are whirled around in 

 diurnal motion (§ 91), we find the current from the north, which 

 meets the Gulf Stream on the Grand Banks (Plate IX.), taking a 

 ^ouihwestwardly direction, as already described (§ 114). It runs 

 down to the tropics by the side of the Gulf Stream, and stretches 

 as far to the west as our own shores will allow. Yet, in the face 

 of these facts, and in spite of this force, both Major Eennell and 

 M. Arago would make the coasts of the United States and the 

 Shoals of Nantucket to turn the Gulf Stream toward the east ; 

 and Sir John Herschel (§ 79) makes the trade- winds, which blow 

 from the eastward, drive the stream to the eastward ! 



124. But there are other forces operating upon the Gulf Stream. 

 The channel of the Thcv are dcrivcd from the effect of chanojes in the 



Gulf Stream shifts n ^ i i i t t i 



with the season. watcrs 01 the wholc occau, as produced by changes 

 in their temperature from time to time. As the Gulf Stream 

 leaves the coasts of the United States, it begins to vary its posi- 

 tion according to the seasons ; the limit of its northern edge, as it 

 passes the meridian of Cape Eace (Plate VI.), being in winter 

 about latitude 40— il°, and in September, when the sea is hottest, 

 about latitude 45-46°. The trough of the Gulf Stream, therefore, 

 may be supposed to waver about in the ocean not unlike a pen- 

 non in the breeze. Its head is confined between the shoals of the 

 Bahamas and the Carolinas ; but that part of it which stretches 

 over toward the Grand Banks of Newfoundland is, as the tem- 

 perature of the waters of the ocean changes, first pressed down to- 

 ward the south, and then again up toward the north, according to 

 the season of the year. 



125. To appreciate the extent of the force by which it is so 

 The phenomenon prcsscd, let US imap^iue the waters of the Gulf 



thermal in its char- i, ° . , 



acter. Stream to extend ail the way to the bottom oi the 



sea, so as completely to separate, by an impenetrable liquid wall, 

 if you please, the waters of the ocean on the right from the waters 



