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 boihng 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 x, y, z, Plate VL 
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, will determine it either 
way. So with the forces of diurnal rotation, and these streaks of 
warm and cool water ; the water that has been to the top and is 
cooled must give way to warmer water that is pressing up from 
below ; it must flow either to the west 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 weight 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 we 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. 
