1922.] Fauna of the Chilka Lake : Observations in Rambha Bay. 687 



only possible to obtain two samples of water at the great majority of the stations 

 namely at the surface and at a depth of four feet. 



As before, observations were taken in a series of traverses across the bay, and 

 the positions of the various stations — numbered 26 to 40 — are shown in plate XU- 

 On this occasion, the prismatic compass used for taking bearings was not so satisfac- 

 tory as the one employed in August, 1919, and in several cases the bearings do not 

 meet very satisfactorily, so that the positions of the stations shown on the plate are 

 to be regarded as approximate only. The results obtained are given in extenso in 

 the Appendix, Table III. 



The first point to be considered is the general density of the water in the bay, 

 and here at the outset we find a most surprising difference from the results obtained 

 in April, 1914. In that year Annandale and Kemp (loc. cit., p. 8) found that the den- 

 sity in Rambha bay was 10 'o except at the southern prolongation near Rambha 

 village, where it was as high as ii - o. A reference to plate XLII shows that in E920, 

 the surface water of the bay was everywhere less than 5 - o, except just at the mouth 

 and in the southern extension at the head of the bay where it was only little over 5*0. 



As was found to be the case in x\ugust, 1919, the surface density shows an appre- 

 ciable range of variation in different areas. In plate XLJI, I have plotted out the 

 various densities, at the temperature in situ, of the surface samples taken at each 

 of the stations. To the north-east of Chiriya Island is an area of higher density 

 that appears to be slowly making its way into the bay. The source of this area is 

 by no means obvious for two observations taken to the north and east of Samal 

 Island {vide samples 94 and 95, Appendix 8, Table III), show that in that region the 

 density of water is on the whole less than that in Rambha Bay. Another area of 

 higher density occurs in the southern extension of the head of the bay, between 

 Rambha village and Gauta Sila, and this I attribute, as before, to evaporation. In 

 the centre of the bay at stations 32 and 33 we find a peculiar circumscribed area of 

 lowered density, 4*5 and under, and a similar lowering of density of the surface water 

 was found at station 35 in the channel between Cherriakuda Island and Barkuda Is- 

 land, though separated from the area in the centre of the bay by a band of water 

 having a density of 458. A reference to the corresponding stations in section 2, 

 plate XXXVI, in which I have shown the densities at standard temperature, shows 

 that at station 32 the lowering of the density on the surface is due entirely to a rise 

 in temperature, for the deusity at standard temperature in this area is uniform with 

 those on each side. As to the cause of this very local rise in temperature I am un- 

 able to offer any explanation. 



Turning now to the results obtained from samples taken at a depth of 4 feet, I 

 have plotted the results, as before, in plate XLJH and here again we find the same 

 areas of increased density both at the entrance and at the extreme head of the bay, 

 while we still get evidence of the area of low salinity in the centre of the bay at sta- 

 tion 32. But, unlike the surface area, the lowered density at this depth is not the result 

 of a raised temperature. It is still clearly seen in section 2, plate XXXVI, after the 

 density has been reduced to standard temperature. No sign of any similar lowering of 



