196 



Records of the Indian Museum. [Yol. XIV, 



do\^ni ])v the villagers in spring and explode with reports like pistol- 

 shots, producing dense clouds of smoke. The floating islands are often 

 reversed and cultivated or made to support pig-styes or even human 

 habitations. 



Intermediate Zone. — On the inner edge {i.e., the edge nearer the 

 centre of the lake) of the Marginal Zone the water, though doubtless 

 less pure than that of the central parts, is clear, and the mud, though 

 black, is less coherent and less malodorous. Submerged thickets of 

 such plants as Ceratophyllum, Hydrilla and TJtricularia flourish, those of 

 Ceratophyllum being particularly luxuriant. This part of the lake may 

 be conveniently considered as an Intermediate Zone, but its boundaries, 

 whether inwards or outwards, are ill-defined. 



Central Region. — In the open central parts of the lake the water is 

 of the most perfect transparency, oxygenation of dead vegetable matter 

 takes place rapidly and completely, and the bottom is composed of 

 minute calcareous particles and fragments of dead plants mingled 

 together to produce a peculiar greyish semi-liquid mud much less solid 

 than good porridge. It has no foul odour. Mr. R. V. Briggs has 

 provided the following analyses of dried mud and of water from this 

 region : — 



Water from Surface in Central Recjion. Mvd from Bottom of Central Ecgion. 



Total solids . 



Organic matter 



Calcium 



Magnesium 



Chlorine 



Sulphate (SO4) 



Silica 



Carbonic Acid (CO3) 



Iron 



''Containing Nitrogen 



-0019 



A considerable part of the Central Region, from which, despite its 

 shallowness, plants growing up out of the water or floating on the surface 

 are practically absent, is filled almost to the surface with thickets of 

 Ceratophyllum, but the bottom in many places is almost bare, with 

 scattered plants of Potamogeton and Hydrilla or with clumps of Chara- 

 ceae, the growth of which seems to choke that of other plants. The 

 Intha fishermen have the custom of protecting the houses occasionally 

 built on poles in the Central Region in connection with fisheries or for 

 other purposes, by floating breakwaters formed of strips cut off from 

 the islands of the Marginal Zone, towed out and anchored by bamboo 

 poles thrust through them into the bottom. These artificial floating 

 islands flourish and produce in their immediate vicinity conditions 

 similar in some respects to those prevalent in the Intermediate Zone, but 

 they are not numerous and their influence is on the whole of small 

 importance. 



