1845.] across the Peninsula from Mangalore. 659 



of Madras. Its locality, according to native information, is about six miles 

 and a half, E. by S. from Tripassore, a little N. of the Madras road, near 

 the village of Permaul Naigpet. It here imbeds ferruginous reniform 

 nodules, and a few pebbles of the older sandstone of Naggery,- and 

 makes an excellent building stone. Like the laterite, it is usually found 

 occupying the higher parts of the undulations which traverse the plains 

 of the Carnatic, in lines running parallel with the eastern ghaut chain, 

 of which great dislocation they probably mark subordinate, synchronous 

 elevatory forces. They are interrupted, usually, by transverse vallies, 

 through which the great lines of drainage from the table-lands pass off 

 to the sea. 



I was unable to find the granite and hornblende rock in situ, but I have 

 little doubt that they are to be found basing the plain. 



Concretionary sandstone sometimes occurs in the loam and silt over- 

 lying the sandstone. 



A little to the eastward of the bund of the tank is a bed of laterite 

 similar to that of the Red hills, the extent of which I had not leisure to 

 trace. It is used for making roads. 



Poonamalee. Between Sri Permatoor and Poonamalee, north of the 

 large Chumbrumbancum tank, a bed of laterite runs to the northward of 

 the road, which in structure resembles that of the Red hills, and another 

 is crossed, or a spur of this, shortly afterwards. 



A third bed is seen between Poonamalee and Madras, near Nabob's 

 Choultry. They afford good material for making and repairing the road, 

 which has been taken advantage of. The laterite enters into the 

 construction of the fort at Poonamalee and St. Mary's Church at 

 Madras; the base of the pedestal supporting the Munro Statue, the 

 construction of the public roads, &c. 



At Madras the soil is sandy, overlying beds of a bluish-black clay 

 interstratified with layers of sand and reddish clay, and occasionally a 

 bed of angular granitic gravel. The whole rests on the solid granite 

 rock. 



