CANADIAN FISHERIES EXPEDITION, lOl'rlo 



241 



And ill its forward progress, the current thus makes a kind of screw movement, 

 exactly corresponding to the screw^ing forwa:.'ds of an ordinary screw, fig. 23 A. 



In the Sargasso sea, tho anticyclonio circuhition is at its maximum in the 

 surface of the sea, the centrifugal force being there at a minimum. The lower 

 portions of the surface layer are flung outwards with greater force than the surface 

 water itself. This gives rise to a screwing movement of the water, the surface water 

 tending towards the centre of the Sargasso sea, and the deep water moving outwards 

 from that centre, as shown in fig. 24. This explains the collection of floating matter 

 in the Sargasso sea. 



Fig. 24. — Movement of the water in the Sasgasso sea. 



This tendency to screw forward is found in all sea currents in high latitudes, 

 as a result of the earth's rotation. But the water of the northern hemisphere moves 

 after the manner of an ordinary right-turned screw; that of the southern, however, 

 screwing towards the left. The screwing tendency increases as sin (^ where (^ is the 

 geographical latitude. Thus, at the equator, it is nil, and has its maximum at tha 

 poles. 



If the water of an intermediate layer is moving in a certain direction, relatively 

 to the layers above and below it, then it will turn off to the right from that direc- 

 tion, until it reaches the right side of the basin, against which it is pressed (fig. 25). 

 Such a current will have its maximum of velocity at the centre, where the water 

 is forced most strongly to the right, returning in the upper and lower portions of 

 the stratum. There will thus be two screwing movements in such an intermediate 



