10 



lagoon a little north of this bed, oysters of similar size and 

 appearance also occur in small clusters scattered sparsely, while 

 everywhere in the vast stretch of very shallow water, i to 1 

 foot deep, which extends eastwards for over a mile from the 

 western shore of the lake between Annamalaicberi and Ivaua- 

 vanturai, single oysters are found here and there, attached in 

 most instances to dead maiti shells, the only foothold available. 

 It is very evident that the presence or absence of oysters over 

 the south end of Pulicat lake is almost entirely a matter 

 dependent upon the presence or absence of cultch ; every 

 suitable scrap bears its colony of these molluscs and it is due 

 to the great scarcity of cultch that the beds in Pulicat lake are 

 so local and so restricted in extent. In this connection we may 

 note that wherever the Canal Engineers have used laterite 

 masonry, as in the revetment at locks and at entrances of canal 

 cuttings into the lake, the blocks under water bear living 

 oysters in considerable numbers. 



II. — Physical Characteristics of Pulicat Lake. 



Before we can be in a position to assess the potentialities 

 offered by the great expanse of Pulicat lake for any form of 

 aquiculture, ostreculture more particularly, we have first to 

 marshal the principal facts in regard to the hydrography of 

 the area. With this aim in view I ran a network of lines 

 of soundings over the lake during my recent visit, took repre- 

 sentative samples of the bottom where necessary, tested the 

 salinity of the water at different distances from the bar, 

 recorded temperatures, and gathered what information was 

 possible anent the effects produced respectively by floods and 

 bv the occasional closure of the sea bar. 



General features and past history. — Pulicat lake is by far the 

 largest backwater on the eastern coast of the Madras Presi- 

 dency. Its drainage area has been given by Russell * (1897) 

 as 1,692 square miles and its high flood waterspread as 178 

 square miles. Its outline may be compared with that of an 

 inverted squat bottle with short neck. The body of the bottle 

 will then represent the inland sea which forms the northern 

 section, Silka lake as it is known locally ; the nook, the wide 

 channel between Karimanal and Annamalaicheri, and the stopper 

 by the contracted channel off Pulicat town. The length of the 

 northern section is approximately 18 miles (from miles 30 to 

 48 on the canal), its width 10 miles. 



History of the Buckingham Canal Project, Madras, Government Press, 1898. 



