128 GEOLOGY OF TRICHINOPOLY, &C. [ClIAP. VI. 



princi25al soil mound is cut through by the torrent coming- down the 

 valley^ and has two good sections, of from 20 to 35 feet in tliickness, 

 of the red sandy loam thus exposed. 



In the middle of this section, on the northern side of a hend of the 

 stream, numerous fossil fresh-water shells are found, all belonging to exist- 

 ing species of the genera Melania, Platior bis, and Lymnea. The shells 

 are in a very brittle condition, and difficult to extract entire. 



Other remarkable accumulations of the red sandy soil in mountain 

 In the Kalroyenmul- valleys occur in the great Toombay and Muttapary 

 '^^' valleys, on the east side of the Kalroyen range. 



On a lesser scale as to size, but very characteristic in form, are the 

 accumulations met with in the horse-shoe valley which opens to the 

 north-east in the KolymuUay, a group of low hills due south of the 

 Godumullay. Here the thickness of the soil is less remarkable than the 

 great number of mounds into which it has been worn by long-continued 

 pluvial action. The same may be said of the last of the accumtdations 

 we will mention, viz., one occurring in the small valley formed by two 

 ridges of no great elevation, which lie between the great Periacombay 

 valley and the main stream of the Peryaur, which rises on the northern 

 end of the KolymuUay range. 



These remarkable heaps of soil would appear to have been formed 

 originally by the combined action of the torrents traversing the valleys 

 in which they occur, and of heavy rains washing down prodigious 

 quantities of soil from the mountain sides, at a period when the annual 

 rain-fall probably far exceeded that at present occurring on this part of 

 India. 



There appears to be further evidence of this having been the case 

 in the dimensions of the beds of some of the torrents on the mountain 

 sides, where blocks, which were at one time constantly exposed to the 

 action of the stream, as shown by the polishing and scratching of their 

 surfaces, are now but rarely, if ever, touched by the water, and are greatly 



( 350 ) 



