ON THE SEA AROUND CEYLON, ESPECIALLY IN THE GULF OP MANAAR. 123 



specific gravity was close on l - 022. At the end of the month, in the Gulf of Manaar, 

 the sea temperature was 82 F., and the specific gravity slightly above T023. 



In February, on the pearl banks, the sea temperatures ranged from 80f F. to 

 84f F, and the specific gravities from 1-0229 to T0239. 



In March, in the same locality, the temperature rose from 83 F. to 8G^ F., while 

 the specific gravities lay between 1'0228 and 1'0234. 



Finally, in April, in the same locality, the temperature rose from 86 F. to 88 F., 

 while the specific gravity was very constant at l - 0228. 



These observations, extending over 15 months, show a range of only 13 F. in the 

 year, 77 F. to 90 F., for the seas around Ceylon ; while in the Gulf of Manaar the 

 lowest and highest recorded temperatures are 77 F. and 88 F. Thurston found 

 the temperature at Rameswaram in July, 1888. to vary from 79 F. to 91 F. 



The specific gravity in the Gulf of Manaar is fairly constant at about l - 023, except 

 at occasional spots; off Chilaw, on 22nd November, 1903, it was T0194, and on the 

 Muttuvaratu Paar in the same month it varied about T0200; while at Galle it is 

 rather lower than the Gulf of Manaar, averaging 1"022, and at Trincomalee it is lower 

 still, 1"019, and at Tamblegam goes down to 1 - 015. 



Further exact knowledge as to the movements of the water over the pearl banks in 

 the Gulf of Manaar is urgently needed. On the " Lady Havelock " we had neither 

 the means nor the time necessary for undertaking this investigation. It is probably 

 the most important matter still requiring settlement, involving as it does the normal 

 distribution of pearl-oyster spat. Till we know more accurately how the surface-drift 

 acts at the chief spatting seasons, we cannot be certain of the source of supply to 

 particular beds, or of the destiny of the larva? produced from our adult oysters. We 

 have not yet the means of arriving at conclusions as to the conditions of wind and 

 weather which are required in order to constitute a favourable spatting season for the 

 replenishment of say the Periya Paar or the Inner Vankali Paar, where young oysters 

 frequently appear. Nor are we able to say with certainty whether the Gheval Paar 

 supplies the Muttuvaratu, or the southern paars replenish the northern, or whether 

 there is any definite relation as to spat-supply between the Ceylon pearl banks as a 

 whole and those off Tuticorin on the Indian Coast. 



We know that there is a general drift of the water over the banks from south to 

 north from about the end of April to the end of September, and from north to south 

 during the height of the north-east monsoon, with intermediate periods of calms and 

 variable winds from February to April and usually again in November. Now it is 

 essential that we should have more definite knowledge as to the resulting surface- 

 drifts in these periods of variable winds between the monsoons, for it is during 

 November and in March and April that the chief spatting seasons of the pearl oyster 

 occur. Information in regard to the stronger and more constant currents which may 

 be sufficient for the purposes of navigation will not suffice for fisheries purposes. 

 We require to know where floating bodies, liberated at certain spots under known 



R 2 



