236 CEYLON MARINE BIOLO(}ICAL llEPORTS 



'J'ho preseuce of an oceanic current from the west during the south-west rnonsoon is a well-established 

 fact. During a weak or moderate monsoon this current never penetrates the gulf at all. It is only when 

 strouix and continued south-west conditions prevail that the oceanic current becomes as it were pushed 

 up into the gulf by the continued effects of strong wind and south-west sea. 



We have already seen that unless the monsoon is very strong there is a northerly current at the 

 head of the gulf, particularly on the Indian side. This northerly current, aided by the -wind, finds an 

 exit through the Paumben Pass, through which a steady current runs to the north during this monsoon. 

 This current through the pass represents the normal flow of water consequent on the monsoon effects 

 in the gulf. When the monsoon is not particularly strong, the oceanic current does not penetrate the 

 gulf, and the Paumben Pass under these conditions provides a sufficient exit for the volume of water 

 wliich is continually being blown into the gulf during the south-west conditions. Consequently the 

 northerly current is felt on the Indian side and on the Ceylon side south of TaUaiviUu Point. We would 

 here point out that the Mannar Channel and the passes through Adam's Bridge become silted up during 

 tlie south-west monsoon. It will be seen that the banks imder lease are situated in such a position that 

 they are protected from this northerly current. What " current " there is on this area is due purely 

 to tlie wind. 



We, therefore, find that bottles liberated off Cape Comorin during a moderate monsoon find their 

 way through the Paumben Pass, and have even been recovered as far north as Cape CaUmere and Tranque- 

 bar ; whilst bottles liberated off the Ceylon coast north of TaUaiviUu Point merely drifted ashore with 

 the wind north of the point where they were hberated. Bottles hberated south of TaUaiviUu Point 

 also merely drifted ashore during a hght or moderate monsoon, and were recovered north of where 

 they were libei-ated. These conditions are, of course, what one would naturaUy expect from the lie of 

 the land. 



During a strong south-west monsoon, however, the currents run quite differently. Then, owing 

 to the force of the monsoon, the oceanic current partly penetrates the gulf, and the water at the head of 

 the gulf becomes piled up. During a strong monsoon the sea level at the head of the gulf is 9 inches 

 above the normal. The exit through the Paumben Pass is insufficient to carry away the volume of water 

 which coUects in the gulf. The stronger and more continued the monsoon, the further into the gulf 

 does the oceanic current penetrate , and the larger the head or cushion of water formed there. This current 

 is purely oceanic, and penetrating the gulf takes an api^roximately east and east-south-easterly course, 

 and reaches the Ceylon coast south of TaUaiviUu Point. It is here joined by a volume of water, which 

 represents an overflow from the head or cushion of water which has become jjiled up in the gulf, due to 

 the penetration of the oceanic current. So that there are two exits for the water which becomes pUed 

 up at the extreme north of the gulf during strong monsoon conditions. There is the Paumben Pass and 

 the south-eastern extremity near TaUaiviUu Point, at which latter point the oceanic current turns south. 

 The drain of water at this latter place, together with the Paumben Pass, provide exits (^vithout 

 producing currents) for the volume of water which has coUected north of where the oceanic current has 

 penetrated the gulf. These exits are merely escapes for the water which has accumulated above its 

 normal level and is therefore under pressure. 



The rate of the oceanic current as it sweeps eastward is • 5 knot per hour. South of TaUaiviUu 

 Point, where it is joined by water which helps to drain away the " laead " of water referred to in the gulf, 

 it obtains a speed of 1 knot per hour. 



Bottles hberated in the height of the monsoon off Cape Comorin and off Tuticorin were recovered 

 at points along the Ceylon coast from TaUai^^Uu Point as far south as Dondra Head ; whilst those Hberated 

 off the Ceylon coast south of TaUaiviUu Point were recovered south of where they were liberated, and 

 those liberated north of TaUaiviUu Point were recovered to the north, having been merely driven ashore 

 with the wind. 



When the oceanic current penetrates the gulf, it becomes evident that the northern current ceases 

 to exist, for it is obstructed by the oceanic current. Those forces (wind and sea) which normaUy produce 

 the northerly set are expended in pushing the oceanic current into the gulf. North of this point of 



