Chap. XII.] soils and supeuficial deposits. 187 



Velur quarry, near Verdachellunij Is an illustration of the former case 

 (Fig. 18). The soil, which in the section is 8 feet thick, rests on the 

 denuded surface of the Cuddalore sandstones, the upper beds of which 

 are much broken up, but are quite distinct from the sand above. The 

 pebbles, chiefly of rolled quartz, are confined to the base of the latter, 

 and at this spot are not very numerous. About a mile further to the 

 North, however, on the slope of the little escarpment described 

 in a former chapter, a section of the same soil is exposed in a 

 nullah about the same thickness as the above, but full of quartzose 

 pebbles of all sizes, from that of an orange downwards, arranged 

 in bands which dip with the surface of the escarpment, or at a 

 somewhat less angle, having apparently formed a beach deposit at 

 some former period. Accumulations of similar pebbles cover the 

 surface of the ground around the Cuddalore sandstone outlier near 

 Chendamungalum, sometimes half imbedded in the red soil, and pro- 

 bably derived originally from the conglomeratic beds at the base of 

 the Cuddalore Group. 



I have seen rolled quartz-pebbles also imbedded in the red soil in 

 some cases in which it rested on gneiss, as at Madripet, in the lower 

 bed of the section given at page 186. 



More commonly on the gneiss the fragments of older rocks imbedded 

 in the red soil are small angular fragments of the local rock. {See Fio-. 

 15, page 180.) In this case, as indeed in all others in this part of the 

 country in which I have found red sandy soil resting on gneiss : I 

 have seen no reason to believe that it is formed by the decomposition of 

 the gneiss in situ. In the case illustrated in Fig. 15, such is certainly 

 not the case, as the gneiss, although much decomposed, is bounded in 

 section by a distinct line of demarcation ; moreover it decomposes 

 into a grey sandy gravel, which is stained near its surface by ferrugi- 

 nous infiltrations from above, so that in any case the iron of the soil 

 must be from a foreign source. 



