26 OEOI.OnY OF TRTeilTXOPOI,Y, &C. [CllAP. 1 f. 



trencling' iiorili and forming a low promontory l)etvveen the alluvial flats 

 of tlie Can very and Vellaur rivers. 



Along this side of the delta^ as well as on the north bank of the 

 Cauvery, west of Seringham Island^ the alluvial houndarj^, owing to the 

 more gentle rise of the country (except in the neighbourhood of the rug- 

 ged granitic ridges of Erungaloor, and the spread of granitoid metamor- 

 phic rocks to the eastward) and the uniform character of the rocks across 



, . ^ , ^ . which the tributaries have worn their way, extends 



AUuvrnm of the tn- 



Lntary streams. £^j, ^ good distance up the courses of these. On 



the south side the boundary is much less sinuous^ the streams having 

 more the nature of torrents than of rivers ; the country through which 

 they flow rising rather rapidly, and being more rugged than that on the 

 left bank of the Cauvery. 



At the Trichinopoly and Tanjore side of the river the alluvium 

 borders the gneiss formation from Caroor to Buttaloor^ one of the sta- 

 tions of the Great Trigonometrical Survey, (now also a station of the 

 Great Southern India Railway,) about 20 miles east of Trichinopoly. 

 Fi'om this point the boundary in an easterly direction runs along grits 

 (Cuddalore sandstones), the cretaceous rocks being absent. About 

 18 miles'^ east of Tanjore the boundary trends south-east, and extends 

 beyond the limits of the sheet. 



Almost the whole surface of the alluvial plain is under wet cultiva- 

 tion, and it is only along the coast, where there are blown sand hills, and 

 in a somewhat elevated sandy tract between Shealli and Tranque- 

 bar, that wet cultivation does not predominate. 



In many places the limit of wet cultivation coincides with the 



boundary of the alluvium, in others it has crossed 

 Cultivation of the allu- 

 vium and covered up the natural line of boundary, ren- 



* The most southerly branch in the delta which, according to the map, leaves tlie Cau- 

 very a little to the west of Tanjore, and crosses the limits of the map (79), is an artificial 

 feeder of the great tank south of Murtiammapooram. 



{US) 



