142 Records of ike Geological Survey of India. [vOL. xil. 
The Vollar (Vellaur) -which rises amoBgthe hills west of the Trichinopoly- 
Madura road, in Lat. 9° 25' and Long. 78° 20', is also very torrential in its charac¬ 
ter, rising suddenly in high freshes of short duration which cut away the hanks or 
excavate side channels. According to the map (sheet 80 of the Indian Atlas), 
the Vellar forks, near the coast, into two branches, represented as of equal size, 
the northern branch being known as the Narasinga Cauvery. How the topogra¬ 
phical surveyors came to show this phenomenon is hard to understand, for it 
does not exist in nature. The northern branch does not occur as shown, the so- 
called Narasinga Cauvery being in reality nothing more than an insignificant 
irrigation channel of such small dimensions that I crossed it repeatedly near 
Arrantangy without noticing it, though I was looking for it. The southern branch 
shown in the map is a gemrine river, 200 to 300 yards wide and of considerable 
depth at flood times. Like the other rivers, in this region the Vellar proper flows 
in a distinctly marked allumal valley, while the Narasinga Cauveiy channel leaves 
the alluvium immediately below its head, and traverses an unaltered tract of 
lateritic sand till it reaches the coast alluvium. 
Next comes the Pambar (Paumben-aur), which rises to the west of Trimicm 
(Tirmium) in Pudukotai. 
Of the throe remaining streams, the Manimut-ar,l or Ti-ipatur river, the 
Serruvayal (Hoop-aur of sheet 80), and the Vaigai, only small portions of their 
courses lie within our area. The Manimut-ar gathers the drainage of the eastern 
end of the Sirumallai, a considerable mountain lying to the north-by-oast of 
Sladura, and of the hills lying north of Nottam in Madura and Trichinopoly dis¬ 
tricts. The Serruvayal rises on the high ground east of the Ti-ichiuopoly-Madtira 
road near Melur (Mailore), and the Vaigai (Vygah) takes its origin at the head 
of the great Cambam valley on the eastern side of the Southern Ghats. The 
headwaters of the Vaigai drain only the eastern scarp of the ghats which re¬ 
ceives but a very limited supply of rain, the watershed of the whole mountain 
mass lying in this quartei’ along the easternmost ridge, hence the rivei' is of 
much less volume and importance than might be expected.® 
The geological structure of the area hero treated of is as simple as its topo- 
Gcological formations g^pl^ical features, all the_ rocks met with being referable 
met with. to but six divisions, which are hero given in their des¬ 
cending order:— 
6. Soils and subaeri.al formations. 
5. Alluvial formations, marine and fluviatilo. 
4. Lateritic conglomerates, gravels and sands. 
<5. Cuddaloro sandstones, grits and congl.->merate3. 
2. ripper Goudwana beds. Hard mottled shales. 
1. Gneissic orinctamorpliic rocks. 
1 The name Vcrshalay-aur given to the Tripatur river on sheet 80 is not recognized by the 
natives for the upper or middle piart of the course. They all call it the Manimut-ar. 
2 A noble project for turning into the Vaigai the surplus waters of one of the principal rivers 
now flowing to waste in the Cochin backwater has been long and earnestly recommended by the 
Madras engineers. As the south-west monsoon rains never fail completely on the higher ridges of 
the ghats, this project of tlrowing a vast supply of water across the present watershed would, if 
carried out, confer an immense boon upon the hot and now too often drought-stricken plains of the 
Mailnni coiinlry. 
