PHYSICAL GEOLOGY. 11 



The remaining lower and newest ridge of all is that of the sand-dunes 



on the seashore, which is entirely subaerial and con- 

 Shore line of sandhills. 



sequently of ever-varying height according to the 



force of the winds. This belt is scarcely noticeable to the north of the 



PenneY delta, while it only obtains any marked width between the outlet 



of the Guditr river (Kandleru) at Kristnapatnam and the Pulicat Lake, on 



the northern shore of which some of the dunes are 30 to 40 feet in height. 



Between this and the chain of sandstone plateaus lies the compara- 

 Intermediate alluvial tively level belt of fluviatile sestuarine alluvium, 

 flat ' a good part of which is really at a lower level than 



the sea. Flooding is prevented by the banks of shore sands and dunes, 

 and by the raised banks of the rivers, though there are still extensive 

 flooded portions in the numerous large back-waters and lagoons, 1 of which 

 the Pulicat Lake is the most striking example. 



Most of the lagoons, and especially the Pulicat Lake, are being gradu- 

 ally silted up, while others to the north of the Penner delta are evidently 

 very much smaller now than they used to be, the deposits from the 

 smaller rivers being of steady accumulation and the blown-sands lending 

 their feeble assistance. Fitful or permanent communication with the sea 

 necessarily delays the silting up for a time, but the levelling up of hol- 

 lows lower than the sea is just as certain a process as the denudation of 

 land that once rises above it. 



Beds and banks of sub -fossilized marine and sestuarine shells occur at 

 shallow depths in this alluvial flat, but not at any decided elevation over 

 sea-level, and these point to a further slight elevation of the country, 

 though it is quite possible that they may have been brought up with the 

 elevation of the Nellore plateaus. 



The drainage system is very simple, there being only two large rivers, 



neither of which, however, rises in this field, and as 

 Drainage system. . . 



this is not very wide, only some 57 miles, the rivers 



1 There are also a few fresh-water lakes, which, however, may possibly have been re- 

 duced in number by the recent extension of the coast canal ; but at the time of my survey 

 in 1869 the long stretches of water at Kapur and Pogaradinna were quite fresh, and the 

 villagers stated that such had been the case for many years. 



( 119 ) 



