124 GEOLOGY OF TRICIIINOPOLY, &C. [ClIAP. YI. 



The various soils which occur over the large area treated of in this 



report may be conveniently referred to the follow- 



Tour classes of soils. . „ , 



ing tour classes : — 



I. Red soils. 



II. Alluvial soils. 



III. Black soils. 



IV. Mixed soils. 



These will be treated of in succession according to their relative 

 importance as they are arranged above. 



First in importance, because covering by far the greatest area, is the 

 ^ Red Soil"* or ' Lai/ the Cevippib man of the 

 TamulianSj which is for the most part a sandy 

 soil, and is perhaps most typically seen on and in the neighbourhood of 

 the Cuddalore sandstones, where it is, on the whole, either the result of 

 the weathering of the sands in situ, or a loose deposit of materials de- 

 rived from the adjacent rocks. There it is a highly ferruginous soil, 

 but occasionally clayey, and then of pale yellow and greyish-brown 

 colours, and on the whole not very productive. Generally it is thinly 

 spread over the surface as in the Woodiarpolliam Taluq, and in the 

 neighbourhood of Vellum ; but instances have been observed where it 

 attains a thickness of 4 feet or more. It is, as a rule, very fine grain- 

 ed, but becomes coarser towards the bottom, Avhere a thin layer of round- 

 ed quartz pebbles is of frequent occurrence. 



The surface is often hardened or caked, the furrows, even in freshly 

 ploughed fields, becoming compacted after some daj-s' exposure. 



Red soil, especially the sandy variety, covers by far the greater area 

 in the mctamorphic regions. Ai'ound the foot of each of the mountain 

 ranges, the red soil occurs in a belt, a mile or two in width, forming a 

 deposit of fine red sand, having a caked surface, like that observed on 

 the soil covering the grits. 



It is generally 4 or 5 feet deep, but a much greater thickness 

 is often observable in the peculiarly deep and narrow gullicp which have 



.(316) 



