46 THE PHYSICAL GEOGRAPHY OF THE SEA. 



off a little way toward the verge of the fountain. Just so with 

 these warmer and cooler streaks in the Gulf Stream. This warm 

 water, in its ascent (§ 57) of five feet to the mile — suppose we are 

 considering the streak which is the hottest, and is, also, the near- 

 est to the American shore — represents the boiling in the fountain ; 

 the warm, ascending water rising up in one body, and the cooler 

 and heavier water going off to the side in another body, to sink 

 and take its place with the other waters of the stream according 

 to gravity and temperature. See the streaks ^, ?/, z, Plate VI. 



59. Now, when these waters come to the top and cool, they are 

 traveling with the current toward the north, and the effect of di- 

 urnal rotation is to turn them, as it turns any other drift (§ 45), to 

 the eastward. They obey this influence to a certain extent, sink- 

 ing down as they obey, in consequence of their greater specific 

 gravity ; beyond this sinking — i. e., farther from the shore — is an- 

 other rising-up place, each thread of the hot water being less and 

 less warm, and each stream of cooler water more and more cool. 

 The forces of diurnal rotation, operating upon the waters as they 

 are successively sloughed off from each thread and streak alter- 

 nately above and below, are quite enough to determine them to 

 the east. A rod being poised on a point at one end, so as to stand 

 alone, has no more tendency to fall to the east than to the west ; 

 but the smallest force, the slightest breath, wdll determine it either 

 way. So with the forces of diurnal rotation, and these streaks of 

 warm and cool Avater ; the w^ater that has been to the top and is 

 cooled must give way to warmer w^ater that is pressing up from 

 below ; it must flow either to the wxst or to the east, and diurnal 

 rotation assists in determining it. When it sinks and reaches its 

 proper level, it must again go to the east or to the west to get 

 into the ascending column, and rise again to the surface in its 

 proper turn. There is no more tendency for it to go to the west 

 than to the east, and diurnal rotation, like the w^eight of the feath- 

 er, is sufficient ; it again plies its forces, and they are obeyed. 



Taking all these facts and views into consideration, we are led 

 to the conclusion with which w^e set out (§ 49), that it is the law 

 of matter in motion, and not the Shoals of Nantucket, that controls 

 the Gulf Stream in its course. 



