256 



DEPARTMENT OF THE NATAL SERVICE 



to the rig-lit, i.e. out from the centre, 

 ment is brought about, vide fig. 41 b. 



x:i 



In this case, then, a cyclonic divergent move- 



i. 



x; 



Fig. 41. — (a) Cycloni*; current about a sinking centre. 



(b) Cyclonic current produced by cyclonic wind. 



(c) Anticyclonic current about a rising centre. 



{d) Anticyclonic current produced by anticyclonic wind. 



If, however, the specific gravity of sea water be diminished by physical change at 

 any point, the water will rise towards the surface, spreading out there in all directions 

 from the rising centre. And the earth's rotation occasioning at the same time an anti- 

 cyclonic circulation, the total movement will then be divergently anticyclonic, fig. 41 c. 

 If, on the other hand, an anticyclonic wind should set the surface water in anticyclonic 

 circulation, then the current will be forced in by the earth's rotation towards the 

 centre, giving rise to a convergent anticyclonic movement, fig. 41 d. 



It is of course obvious, that a current concentrating upon a given centre will be 

 far more strongly marked than one spreading its waters out in all directions. A cur- 

 rent occasioned by cyclonic wind will therefore be but slightly perceptible, while those 



