Chap. III.] post-cretaceous rocks. — (cuddalore sandstones) . 45 



but in this area highly ferruginous varieties of gneiss are ahnost un- 

 known, quartzose or felspatho-quartzose gneiss forming the great mass 

 of the country. 



3rd. — The position of the bed of laterite and its conglomeratic 

 structure (containing rounded and sub-angular fragments of quartz) are 

 two points, both of which are opposed to the decomposition in situ hypo- 

 thesis. The occurrence of rounded fragments (almost pebbles) of quartz 

 in the conglomerate cannot be explained by supposing the edges to have 

 been blunted by weathering ; but there is no difficulty in obtaining an 

 explanation if we refer the phenomenon to a process of attrition previous 

 to deposition, the whole of the materials composing the laterite appearino* 

 to have been conveyed from a distance. 



As before mentioned, there seems reason to consider this bed as 

 having been originally continuous with the superficial laterite occurring 

 at Vellum, and therefore as a continuation and thinning out of the 

 laterite westward, as sho^vn in the Section at page 42.''^ 



The flora on the grits formation is characteristic of an extremely 

 dry soil marked by the absence of trees requiring much moisture, such as 

 cocoauut, palms, and bamboos, and the occurrence of extensive jungles of 

 low, scrubby, prickly shrubs, as to the south-west of Cuddalore and at 

 Ammahpettah, and of large topes of the Palmyra-palm. Jack trees thrive 

 admirably around Verdachellum, and topes of large fine Mango and Elli- 

 poo (Bassia longifolia) trees are not uncommon. Where an abundant 

 supply of water can be got, rice cultivation is carried on, and the soil 

 seems not unfruitful ; but compared with the alluvium, the whole country 

 has a barren aspect. The surface is level, or only slightly undulating, 

 without any rise worthy of the name of a hill. 



* A similar relation probaT)ly subsists between the two small outliers of laterite occurriug at 

 Auawari, 4 miles south-east by south of TiruvananwUur, and the grits-plateau of Cuddalore. 



( ^267 ) 



