384 THE DEPTHS OF THE SEA. [CHAP. vm. 



to it. But as for the seat of the forces which put 

 and keep the Gulf-stream in motion, theorists may 

 place them exclusively on one side of the ocean with 

 as much philosophical propriety as on the other. 

 Its waters find their way into the North Sea and 

 Arctic Ocean by virtue of their specific gravity, while 

 water thence, to take their place, is, by virtue of its 

 specific gravity and by counter- currents, carried back 

 into the gulf. The dynamical force which causes the 

 Gulf-stream may therefore be said to reside both in 

 the polar and in the inter tropical waters of the 

 Atlantic." 



According to this view, the tropical water finds its 

 way on account of its greater weight towards the poles, 

 while the polar water, owing to its less weight, moves 

 southwards to replace it. The general result would 

 be of course a system of warm under- and cold 

 surface-currents, and these we do not find. I merely 

 quote the passage as a curious illustration of the 

 adage that on most questions a good deal can be 

 said on both sides. 



We have already considered the doctrine of a general 

 oceanic circulation, which has been so strongly ad 

 vocated of late by Dr. Carpenter, and I have merely 

 to advert in this place to the bearing which that 

 doctrine has upon our views as to the origin of the 

 Gulf-stream ; its bearings on the extension and dis 

 tribution of the current will be discussed hereafter. 

 As already stated, Dr. Carpenter attributes all the 

 great movements of ocean water to a general con- 

 vective circulation, and of this general circulation 

 he regards the Gulf- stream as a peculiarly modi 

 fied case. In the passage already quoted (p. 370) of 



