335 



GeoloQi/ of (he South of India. 



[Oct. 



ered by tlie debris of a shelly coiigloinornte, much more indurated 

 and inipregnated with green earth, exhibiting; cavities and shells iji 

 relief: from the shape of the former, there can be no doubt of their 

 ha\ing: once contained shells. Some of tiie shells are entire, but 

 are rarely Hvittened. The matrix appears to be siliceous, and, in 

 some cases, approaches to imperfeel iieliDtropc. It is not fusible 

 before the blowpipe." 



'•I may here mention that, in a report to the Marquis of Hastings, 

 in June, 1819, 1 mentioneil the existence of shells in trap rocks at 

 Mtdconda, at a heiicht of two thousand feet above the sea. The 

 hill was composed of nudular-trap, and lyini^ on its surface, were 

 numerous pieces of sdiceous stone, cont.nninj^ shells of the genera 

 turbo and cyclosioma — the specific gravity of the stone varied from 

 2-0 to *2-5 : the shells did not effervesce in acids, although some of 

 them preserved their external polish. Internally, some of the stones 

 appeared to pass into flint, particularly those of small specific gravi- 

 ty, whilst their external surface effervesced in acids. Some of the 

 small shells were completely changed into ca lcedon y. Speci- 

 mens of these shells are lodged w^ith the Asiatic Society." 



*' It is a remarkable fact, that the only remains of animals hitherto 

 discovered in India, should be found in trap rocks, and under quite 

 peculiar circumstances. 1st. They are found in situations where 

 there are no indications of the former existence of lakes. 2d. Both 

 the shells and matrix are destitute of carbonic acid. 3d. The former 

 are, in many instances, squeezed flat without fracture, and, in some 

 cases, completely commixing with their matrix." 



" These effects could only have been produced by the agency of 

 heat, and, consequently, the modern theory of sub-marine or sub- 

 aqueous volcanoes, will best serve to explain the phenomena. 

 These shells were deposited in the stratum of clay in which they 

 are now found, and when forced up by the mass of wacken beneath, 

 they were, most probably, at the same time covered by the nodular 

 basalt. Thus we have heat, to drive off the carbonic acid and soft- 

 en the shells under a pressure, which assisted the process, and, at 

 the same time, flattened them." 



" 1 have too numerous collateral proofs of the intrusion of the trap 

 rocks in this district, amongst the gneiss, to allow me to doubt of 

 their volcanic origin. I shall take an early .opportunity of complet- 

 ing the history of the trap rocks of India, for which I have collected 

 materials for several years past." 



