8 F06TE : GEOLOGY OF MADURA AND TINNEVELLY DISTRICTS. 



4. Liiteritic couijlomeratps, gi-avels and sauds. 



3. Giitty sandstones, (Cuddalore or Rajamandri beds, Con]evarain gravels). 



2. Gondwana rocks (Jurassic) ? 



1. Gneissic rocks. 



Owing to tlie general flatness of the sea-board in many parts of 

 the country nearly up to the foot of the mountains, the streams all 

 flow in wide shallow valleys, and there is consequently a remarkable 

 want of good sections of the rocks of all ages, — a condition of things 

 which has necessarily rendered the working out of the several formations 

 much more difficult and their correlation so much the less satisfactory. 



The whole gneissic area falling within the limits of the map accom- 

 Note regarding the Ponying this memoir has been shown in colour, 

 ^'^^V- though not entirely surveyed in detail ; the 



tracts surveyed in detail being represented by a darker tint. The 

 tracts not actually surveyed in detail are however not unknown; 

 many of them are traversed by high mountains and hills, the obvious 

 continuations of gneissic beds well known and carefully examined 

 within the surveyed areas. The eastern scarpg and spurs of the Siru- 

 malai, the eastern spurs of the Palani mountains^ and the bare scarps of the 

 great Varshanad spur of the Southern Ghats show innumerable exposures 

 of rock, which even the untrained eye cannot help recognising as exten- 

 sions of the known gneissic beds. Further south in Tinnevelly district, 

 beginning with the great Saddaragiri spur, great part of the western side 

 of the district was crossed by me in various traverses made during a visit 

 paid to the south in 1869. The country around Sri villiputtu rand thence 

 south along the foot of the ghats to Kuttalani (Courtallum) was tra- 

 versed, also the line of country lying between Srivilliputtur and Kutta- 

 1am via Sankaranainarkoil. I made various trips among the moun- 

 tains west and south of Kuttalam (Courtallum) — a traverse from that 

 place to Palamcotta, visits to the upper valley of the Tambraparni at and 

 above Papanasam, to Arabur and Sherraadevi, to the Singampatti valley 

 and falls, and lastly to Tirukurungudi (Tricknangoody) and up the moun- 

 tains to the Asambu plateau. Although I recorded no geological obser- 

 vations made during this trip, I became sufficiently acquainted with a 

 ( 8 ) 



