236 Further Observations on the 



fragments of the rock which strew the ground. As all these 

 therefore have either been washed out or otherwise detached 

 from nearly the upper part of the formation, it is difficult 

 to form an estimate of the vast reservoir of organic remains 

 which the rock must still contain beneath its surface. We have 

 already seen, that where an occasional stream of water, 

 existing only perhaps during the height of the monsoon, 

 had worn itself a channel down the brow of the hill at 

 Seedrapett, many of the stones which it exposed were petri- 

 fied Nautili and Ammonites, and this is probably a criterion 

 of what an excavation would bring to light. 



In a paper by Dr. Malcolmson, which appeared in the 

 Transactions of the Geological Society, (2d series, vol. v.) and 

 was reprinted in the Madras Journal of Literature and Sci- 

 ence for July 1840, there is the following passage : " With 

 regard to the age of the silicified wood of Pondicherry, no 

 facts have yet been ascertained, which can justify any conclu- 

 sion. It is however to be hoped that a gentleman familiarly 

 acquainted with the tertiary and volcanic rocks of Greece 

 and Italy, will soon communicate positive information re- 

 garding the geological, relations of the sandstones contain- 

 ing the silicified wood and the fossil shells, the conical 

 hollows, obsidians, and other indications of volcanic action 

 said to exist in that neighbourhood." I am not aware to 

 whom Dr. Malcolmson alludes; but if the gentleman in 

 question has succeeded in making any discoveries regard- 

 ing the shells and other fossils at Seedrapett and Trivacary, 

 they have never been divulged. Owing to the absence of 

 sections, and the want of means of penetrating the hard sur- 

 face of the limestone rock, we can only guess that it rests 

 upon the sandstone containing the silicified wood, and thus 

 perhaps the required clue as to the age of the whole forma- 

 tion has been obtained. There is no granite or other igne- 

 ous rock within the. area covered by the limestone, the 

 nearest rock of that description being a dark granite, which 



