Chap. VI.] superficial deposits and soils. 123 



The greatest development of both of tlie above forms of kunkur 

 has been observed, as might be expected, in those parts of our area in 

 which hornblendic gneiss or basaltic trap prevail, there being about seven 

 per cent, of lime in hornblendic rock, while as much as nine per cent, 

 of the same mineral occurs in some basalts. In the neighbourhood of 

 Vellyana, about 8 miles south of Caroor, there has been a great de- 

 position of this rock, hornblendic gneiss occurring there to some extent, 

 accompanied by basaltic trap ; it is also pretty frequent in the neigh- 

 boiu'hood of the crystalline limestone further south, while over the 

 whole of the country north of the Cauvery, instances of the several forms 

 of the deposit may be frequently seen. Kvinkur is generally of a dirty 

 white colour where pure, but the presence of iron renders it brown 

 or reddish in hue. It occasionally assumes a pisolitic or botryoidal 

 form, and is then of reddish-brown or dark brown colour, and very 

 compact. 



As regards the age of this deposit, as far as we have seen, it would 

 appear to be essentially recent, and there can be 



Ao'p of liiiiijctii' 



little doubt but that the formation of all the vari^ 

 ties of kunkur mentioned above is now in progress in every part of the 

 country where calciferous rocks are being acted on by atmospheric agen- 

 cies. It was seen in one case overlying the cotton soil, on the west bank 

 of the Conari river, which runs to the north past Thavyur, in the neigh- 

 bourhood of Volcondahpuram, where a gritty deposit of gneiss particles 

 in a matrix of kunkur lies on the gneiss, and is spread over the adjacent 

 cotton soil to some small extent. 



Kunkur pebbles formed by the wearing down of angular fragments 

 or of large concretions may be found in the upper courses of several of 

 the larger rivers and streams in considerable quantity. 



Soils. — Under this head we include, irrespectively of their origin, 

 those formations generally but slightly coherent which form the upper 

 surface of the country^ and therefore come under the hands of the 

 agriculturists. 



(olo) 



