2 Recnrds of the Indian Mvseinn. [Vol. XIY, 



side a rather larger stream enters the lake by several mouths, coming 

 also from the north-west, and rising in the high ground that separates 

 the watershed of the Irrawaddy from that of the Salween. Before 

 reaching the lake, and on the other side of a range of hills, it disappears, 

 running for some miles at a great distance beneath the surface. This is 

 a habit of rivers on the Shan Plateau, a habit that may have had consi- 

 derable influence in the distribution of the fauna. On the eastern side 

 a few hill-streamlets enter the lake ; many of them dry up in winter, 

 and all are very short. From the south end of the lake a larger river 

 makes its way southwards ; like the stream on the western side it 

 disappears into the ground, but at some considerable distance south 

 of the lake. Its subterranean wanderings are unknown, but there can 

 be little doubt that much, if not all. of its water finally reaches a tribu- 

 tary of the Salween. 



The lake is thus, in a sense, the centre of a closed system, without 

 direct communication with any of the important river-systems of Burma, 

 but, in a wider sense, it may be considered to belong to the system of 

 the Salween. 



For reasons that will be made clear shortly, it is impossible to state 



the dimensions of the Inle Lake precisely. It is 



' about 14 miles long, and about 4 miles broad. 



The depth varies with the seasons. In March it is nowhere greater 



than 12 feet, and the average depth is not more than 7 feet ; but at the 



end of the rainy season the greatest depth must be at least 20 feet. 



The water is remarkable for its extreme clearness. It is thus possible, 

 when there is no breeze, to watch the animals at 

 ^^' the bottom almost as if they were in an aquarium. 



All the silt brought down by the streams is deposited before it reaches 

 the middle of the lake. The clearness of the water is probably correlated 

 with its chemical composition. Mr. R. V. Briggs has analysed a sample 

 which came from the surface in the middle of the lake, with the follow- 

 ing results : — 



Per litre. 



Total Solids 0-1710 



Organic matter ........ 0-0160 



Calcium 0-0222 



Magnesium 0-0279 



Chlorine 0-0017 



Sulphate (804) 0-0017 



Silica 00010 



Carbonic Acid (CO.,) 0-1030 



Iron ...... Less than 1 part in million. 



No precise details are available as to the temperature of the water. 

 We found it remarkably constant at the beginning of March, not vary- 

 ing more than 2 degrees Fahrenheit. The average surface temperature 

 was about 71°F. (21-7° C.) at that season, and the average bottom 

 temperature one degree Fahrenheit lower ; the average air temperature 

 being about 73°F. (22-8° C). 



