4 foote: geological structure oe the eastern coast. 



Except the Kistna all these rivers receive their principal supply from 

 the north-east monsoon rains ; but the south-west monsoon rains appear 

 to be heavier than in the latitude of Madras. The north-east monsoon 

 is, on the contrary, lighter in this part of the peninsula than further to 

 the south. Owing to the greater width of the peninsula, the westerly 

 winds acquire a considerably higher temperature than at Madras, and 

 begin to blow earlier in the season. 



The several geological formations occurring in the area under con- 

 sideration may be conveniently grouped as follows, 

 Geological formations. . 



in descending order : — 



fl. Soils and subaerial deposits. 

 Recent ... < 6. Alluvia, marine and fluviatile. 



(. 5. Lateritic, sand and gravels. 

 Tertiary ... 4. Cuddalore (Rajahmundry) sandstones and conglomerates. 



fPavulur and Chebrole sandstones. 

 Mesozoic... 3. Upper Gondwana V Vemavaram shales . 

 Series. J 



C Budavada sandstones. 



f 2. Kadapa Series. 

 Azoic ... <1. Gneissic, or Metarnorphic Series, and intrusive rocks included 

 (. in it. 



In describing these several formations, it will be best to take them accord- 

 ing to their respective ages in ascending order. 



Before passing to their detailed description, it will, however, be well 

 to give a few notes on the geological information 



"Previous od servers 



that had been collected and published prior to the 



geological survey. 



The earliest known geological notes on our area are those published by 



Dr. Heyne 1 in 1814, in the maps accompanying 

 Dr. Heyne. . 



which he attempts to show roughly and partially 



the " geological situation" of the country. His geographical basis 



i Tracts, historical and statistical, on India, by Benjamin Heyne, M.D., f.l.S., &c, &c. 

 Naturalist on the Establishment of Fort St. George, London 1814. Of the two maps given, 

 the first is far the more correct in its delineation of the rivers and mountains along the 

 eastern coast. 

 ( 4 ) 



