258 CEYLON MARINE BIOLOGICAL REPORTS. 



Such, in brief, is the present method of inspection, which has led to the more accurate charting of 

 the rocky areas knowTi as paars, and. as pointed out above, also gives the correct configuration of oyster 

 beds as well as the rock. 



7. — Gener.'VL Observations and Remarks. 



On \-isiting the pearl banks for the first time one is struck wth the distance which the banks 

 pi-opev — such as the Cheval Paar — are from tlie land, and tlie featurelessness of the coast, which is here 

 very low-lying. 



The only conspicuous well-defined landmark is Kutrimalle Hill. The absence of other landmarks 

 has been remedied by the erection of masonry towers, obelisks, and, of late, beacons, as described else- 

 where. All landmarks are clearly seen after noon, but owing to the low elevation of the land, station 

 or position buoj's have had to be used to iirolong hues of positions to the more northern paars in order 

 to ensure accuracy. On such distant landmarks a sHght error means perhaps half a mile out where an 

 object is from 14 to 20 miles distant, as in the case on the Periya Paar Karai and the true Vankali Paar. 

 Here a system of alinement and transit bearings has been adopted, together with masthead angles, 

 ensuring accuracy where the landmarks are so distant ; but we have the two new beacons, i.e., Aripu and 

 VankaU reef beacons, to work \rith. 



On the southern paars, i.e., those south of Kutrimalle Point, starting from the northern extremity 

 of Karati vu Island , this difficulty ceases , as the mainland has a good elevation. The paar groimd , includ- 

 ing the Karati vu, Alanturai, Krusadai, and Muttuvaratu Paars, is bounded on the west by the overfall, 

 which here approaches to wthin 6 miles of Karati vu Island, so that all landmarks are clearly visible, 

 both those on the mainland and on Karativu Island. 



All nautical data accumulated during the last eight years, together with that obtained from the 

 Admiralty chart of the Gulf of Mannar, the latest Government chart of the pearl banks, and other data 

 obtained personally, has been co-ordinated within the last year, and are sho-mi on a preUminary chart 

 which has been drawn up of the whole area imder lease. This chart embodies aU nautical data collected 

 up to date, and also shows the paar or rocky gromid as revealed by the latest inspection, which, with the 

 rectangular method of inspection as described, took the form of a survey. The chart also shows the 

 fauna of the entire area, which has been determined by the Scientific Adviser to the Company ; it is 

 therefore a nautical and biological chart. 



I may mention here that the positions of aU landmarks have been fixed and verified from a base 

 hue between Armiakalu and Kutrimalle towers. The positions of these trigonometrical stations were 

 furnished by the Government Survey Department on the latest chart of the pearl bank area. In addition 

 to the above, a survey has been made of Dutch Bay, and a chart on a scale of 4 inches to one nautical 

 mile drawTi up. 



Investigations on superficial currents in the Gulf of Mannar and immediate vicinity have been 

 uiade and are being continued, which we have every reason to beheve are of considerable importance, 

 and wiU throw more light on the origm of exotic spat, which from time to time replenish the banks, the 

 intermittency of wliich accomits for the failure of fisheries. These investigations are being made from 

 independent data, together with information obtained from the hberation of drift bottles and the 

 collection of planktonic forms over long periods of time. 



An experimental nursery has been erected in the sea, under the lee of the Silavatarai reef. Un- 

 fortxmately the depth of water is only 12 feet on this protected area. The nursery is built of expanded 

 metal with railway iron uprights. It has %\ithstood the south-west monsoons well, and answers aU the 

 purposes for which it was intended. 



A masonry tank has been erected on the foreshore at Marichchukaddi , and is' filled by a pump 

 fitted with a filter. The pipe is carried well out clear of the foreshore into deep water. A second tank 

 has been also fitted, and apphanees — drain pipes, &c. — such as are necessary for the experimental 

 scientific work carried on. 



During recent trawUng operations for certain fish required for scientific experimental work the 

 small number of fish on the banks at present was apparent, and is incident doubtless on the absence of 

 oysters and other shell fish. 



