GEOGNOSY OF PENINSULAR INDIA. 243 



of Bengal ; this eastern range may be said to terminate at 

 the same latitude as that of the commencement of the 

 western. Granite and syenite appear to form the basis of 

 the whole of these eastern ranges, appearing at most of the 

 accessible summits from Cape Comorin to Hydrabad. Rest- 

 ing upon them are various primitive and transition stratified 

 rocks, as gneiss, mica-slate, quartz-rock, clay-slate, chlorite- 

 slate, talc-slate, potstone, serpentine, graywacke, and lime- 

 stone. In many places there are extensive deposites of a 

 red sandstone, and also some partial displays of overlying 

 trap. 



The flat country of the Carnatic, that is of the country 

 east of the Ghauts of Mysore as far as the Pennar river, 

 seems to consist of the debris of granitic rocks, with plains 

 of sand and mud, probably left by the retreating sea. In 

 confirmation of the former presence of the sea in the tract 

 now occupied by the flat lands the following fact may be 

 menti^Dned : — On digging a garden about two miles from 

 the seashore at Madras, from the surface, for five feet, there 

 was a stratum of brown clay, chiefly intermixed with sand ; 

 then followed a stratum of bluish-black clay, in which, at 

 the depth of twenty-one feet, was a thin and scattered layez 

 of large or/ster-shells, all lying in a horizontal position ; into 

 the lamina composing the shell the black clay had penetrated, 

 so that they split asunder with great facility. There were 

 also shells of the cockle and other kinds. At the depth of 

 twenty-seven feet springs began to gush, the stratum be- 

 came softer, and more and more mixed with quartz-sand, 

 still, however, of a dark slate-colour. This continued to 

 the depth of thirty-seven feet. In the neighbourhood of 

 Pondicherry are beds of compact shelly limestone, and some 

 remarkable silicious petrifactions, said to be chiefly of the 

 tamarind-tree. These deposites at Madras and Pondicherry 

 are considered to be tertian,'. The bed of the Cavery, or 

 rather the alluvial deposites in the vicinity of Trichinopoly, 

 afford gems corresponding to those found in Ceylon. In 

 approaching the Pennar the laterite formation expands over 

 a larger surface, and clay-slate and sandstone begin to 

 appear. The river-districts of the Pennar, Krishna, and 

 Godavery are based on granite, syenite, and various primi- 

 tive stratified rocks, all of which are frequently traversed 

 by veins and overlaid with masses of trap. Upon the 



