130 GEOLOGY OV TllICniNOPOLY_, &C. [ChAP. VI. 



to be almost entirely formed by decomposition of tlic quartzo-felspathic 

 rock in situ. It contains occasionally scattered pellets of laterite charac- 

 ter, probably resulting from the decomposition of grains of magnetic iron 

 dispersed at rare intervals through the parent rock. 



Of the origin of the red soils, we can say but little ; a great part, 

 and probably by far the greater part, is formed from 

 ° ' the decomposition of more or less ferruginous rocks, 



especially the hornblendic varieties. Mr. Blanford considers them to have 

 been chiefly formed in or on the sides of lagoons, — a supposition which does 

 not, however, appear to us to be borne out by the facts of the case gener- 

 ally, though to certain beds of limited area such an origin may be attributed* 



The red soils occurring on the several ranges of mountains which are 

 evidently formed by weathering of the underlying rocks, cannot be dis- 

 tinguished by the eye from the Lai of the plains, and in both, the varia- 

 tion of the amount of ferruginous matters may be constantly seen to be 

 dependent upon the nature of the underlying rocks. 



II. Second in importance in point of area are the alluvial soils, 

 which have, however, already been described in full in the Ilird Chapter 

 as members of the youngest of the Geological systems found within our 

 area of report. 



III. Blach soils. — Cotton-soil (or Regur) as the name implies is 



one on which cotton is grown. But it does not 

 follow that this vegetable product is only grown on 

 such a soil ; indeed, it is, in the districts treated of, oftener and better culti- 

 vated on a dark grey soil, in which there is a considerable amount of cal- 

 careous matter (kunkur) . The Regur, which is known to the Tamidians 

 by the name of " Karuppu-man" (black soil), and to the Telugu-speaking 

 Hindoos by the name oiregada, (a soil identical with that of the Dhoor 

 plain, Cuddapah district, which is one of the typical cotton-soil areas in 

 south India,) covers considerable areas of the country we are dealing with; 

 the largest unbroken or nearly unbroken spread occurring in the southern 

 ( 352 ) 



