INTRODUCTORY. 3 



The central and southern parts of the Southern Ghats tract require 



but very brief mention here beyond their general 

 The Southern Ghits, "^ , ,. p • -,, -,^. • 



central and southern influence on the chmate of Tinneveily District and 



^^^ ^' the fact that they feed the sources of all the more 



important southern rivers. 



Hydrology. — The hydrology of the two districts is as simple as the 

 Rivers in Madura dis- Orography, as all the rivers flow to the east or south- 

 *'"^*^' east. The Varshalei or Mauimutar, the Seruvayal 



or Up-ar (Salt river; Hoop-aur of sheet 80), and the Vaigai which drain 

 the northern and central parts of Madura district flow into the Bay of 

 Bengal through Palk's bay. The southern part of Madura district is 

 drained by the Gond-ar, which debouches into the Gulf of Manaar, 



The drainage of Tinneveily district is effected by the Yaippar in the 

 Rivers in Tinneveily north^ the Tambraparui in the centre, and in the 

 *^-^^*^''^*- south by three small rivers— the Nat-ar or Kara- 



meni-ar, the Nambi-ar, and the Hanamanadi. 



Of the several rivers enumerated above only one, the Tambraparui, 

 Water-supply of the comes really under the influence of the south- 

 Tambraparni, j^Q^i monsoon and obtains a steadily sustained 



supply of water dm-ing the continuance of the summer rains. The reason 

 of this is that the Tambraparni, and to a lesser extent its main northern 

 tributary, the Chittar, have their headwaters rising well within the 

 limit of the area over which the rain clouds rest continuously. The 

 positions occupied by the clouds during the south-west monsoon appear 

 at first sight to be somewhat capricious, but they are doubtless in great 

 measure due to currents of air caused by the peculiar configuration of the 

 mountain masses, which mostly terminate eastward in very abrupt and 

 precipitous scarps. The clouds, which cover the mountains, often for 

 weeks together without lifting entirely, lie banked up along the water- 

 shed, or extend but little to the eastward of it. 



Except in the case of the Tambraparni, unfortunately for the 

 Madura and Tinneveily plains, the watershed is mostly close to, or 

 coincident with, the top of the eastern scarp -, hence nearly the whole 



( 3 ) 



