6 GEOLOGY OF TUICllINOl'OLY, &C. [ChAP. I. 



attain a sufficient size to stand much higher than the surrounding 

 jungle. 



South of the line above defined as extending from the Kalroyen 

 range to the Madras road near to Arsinoor the country becomes 

 more undulating^ being cut into numerous ridges and furrows by 

 the valleys of the Munimootaur and many other tributaries of the 

 Vellaur rising in the above range. The country south of the Vellaur, 

 sloping from the Patchamullays eastward, is very similar in its 

 appearance, but a little less undulating in character. There is but little 

 jungle on this undulating country, excepting quite close to the base 

 of the Patchamullays. The same may be said of the rudely triangular 

 area lying between the hills of the Ahtoor Pass and the confluence 

 of the Vellam* and Pereyaur. Eastward of the Madras road the char- 

 acter of the surface becomes more and more tame, and it soon sinks 

 into an almost dead level, excepting where broken by the low scarj)s 

 of the small plateau of rocks belonging to the Cuddalore series, (see 

 further on,) which rest on rocks of the Cretaceous period. 



The scarps of these plateaux, although low, form rather marked 

 objects on the northern and southern boundaries of the alluvial valleys 

 of the Aiiankup, Punniar, and Vellaur rivers. The surface of these 

 plateaux where not cultivated is covered by low, scrubby, and often 

 very thorny jungle. These plateaux in most parts terminate suddenly 

 to the eastward, the alluvium resting against the foot of low lines of cliff. 



Southward of the most extensive of these plateaux (that of 



Woodiarpolliam) the delta of the Cauvery forms 

 Delta of the Cauvery. 



an immense plain sloping down to the sea at so 



sliglit an angle as to present to the eye the appearance of an absolutely 



dead level."^ This great plain is no where broken by the smallest 



* The whole of this vast alluvial plain is so much cut up by irrigation channels, 

 and the area under wet cultivation is so immense, that progress is generally impossible, 

 except along the causeways or the high roads traversing the districts between the various 

 important towns. 



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