38 CRETACEOUS HOCKS OF 8. INDIA. [ParT II. § 1. 



with that of the gneiss, and, lastly, the intense toughness of the rock 



itself and its slight tendency to break up into fragments of such size as 



could be easily transported by ordinary marine action. 



The aspect of the low country of Trichinopoly on the gneiss, as on the 



Cretaceous rocks, is gently undulating and bare 

 Aspect of country. ^ o ^ o 



of vegetation, and except in the occasional occur- 

 rence of small bosses and low hills, such as I have described, the former 

 differs but little from the latter. The vegetation depends more on the 

 nature of the soil than on that of the underlying rock, and except a 

 narrow strip at the foot of the hills, both the gneiss and the Cretaceous 

 rocks are covered for the most part with black regur, which, from the 

 water-shed of the Cauvery Northwards to the Vellaur, covers the country 

 so thickly that but little of the underlying rock is anywhere exposed. 

 In the drainage basin of the Cavivery the denudation has been greater, 

 the average level of that river being much below that of the Vellaur, and 

 the fall of the country which it drains on either side in consequence more 

 rapid ; and it is in this part of the district that the most complicated and 

 interesting features of its Geology are seen. To these I shall now return, 

 commencing my description with that of the oldest of the stratified 

 portion of the series, the plant beds near Ootatoor. 



